Author + information
- Received October 30, 1997
- Revision received February 6, 1998
- Accepted February 18, 1998
- Published online June 1, 1998.
- Peter Boekstegers, MDa,* (, )
- Wolfgang Giehrl, MDa,
- Georges von Degenfeld, MDa and
- Gerhard Steinbeck, MDa
- ↵*Address for correspondence: Dr. Peter Boekstegers, Medizinische Klinik I, Klinikum Grosshadern, Universität München, Marchioninistrasse 15, 81377 München, Germany
Objectives. We sought to study the safety, feasibility and efficacy of selective suction and pressure-regulated retroinfusion to protect against myocardial ischemia in patients undergoing normal risk and high risk balloon angioplasty.
Background. In a pig model of acute myocardial ischemia it was previously shown that use of selective suction and pressure-regulated retroinfusion was able to substantially preserve regional myocardial function during ischemia with a higher efficacy than that obtained with unselective synchronized retroperfusion.
Methods. In 42 patients with normal risk (n = 27) or high risk (n = 15) percutaneous transluminal coronary angioplasty (PTCA), alternate balloon inflations of the left anterior descending coronary artery (60 s) were either supported or not supported by selective suction and pressure-regulated retroinfusion of the anterior interventricular vein. In an additional group of 10 patients with normal risk, retroinfusion was directly compared with autoperfusion during 10 min of ischemia.
Results. Balloon inflations without retroinfusion resulted in a decrease of regional myocardial function in the ischemic zone to 13% of baseline. In contrast, regional myocardial function was preserved at 76% of baseline (p < 0.05) during balloon inflation supported by retroinfusion. This preservation of regional myocardial function by retroinfusion was maintained during 10 min of ischemia with at least similar efficacy compared with autoperfusion. With retroinfusion, hemodynamic variables were stabilized in normal risk and high risk patients. No complications related to the catheterization of the anterior interventricular vein using a femoral approach (95% success rate) were observed, and clinical follow-up after 3 to 6 months was uneventful with regard to the coronary intervention.
Conclusions. Use of selective suction and pressure-regulated retroinfusion was feasible and safe and had a high efficacy for preserving regional myocardial function and hemodynamic variables during PTCA in normal risk and selected high risk patients.
Synchronized retroperfusion of coronary veins was able to partially reduce myocardial ischemia in patients undergoing percutaneous transluminal coronary angioplasty (PTCA) (1,2). The efficacy of synchronized retroperfusion, however, was too low to completely prevent loss of regional or global myocardial function. In recent experimental and clinical studies, retroperfusion was combined with intraaortic balloon counterpulsation or extracorporeal circulation to enhance its efficacy (3,4). Although such a combination of regional with systemic support devices may compensate for insufficient myocardial protection with each system alone, clinical application is limited by these time-consuming procedures and their unacceptably high complication rates (5–8). In contrast, a retrograde support device with sufficient efficacy might combine regional myocardial protection with preservation of systemic hemodynamic variables, keeping its application simple and the complication rate low.
In previous pig studies, preservation of regional myocardial function and myocardial oxygen tension was substantially higher using selective suction and retroinfusion of coronary veins compared with synchronized retroperfusion (9). Because of the more selective approach and the rapid squeezing of the coronary veins before retrograde blood supply, the efficacy of retrograde nutritive perfusion was probably increased (9,10). Furthermore, the addition of pressure regulation to the system of selective suction and retroinfusion provided an adaptation of retrograde blood flow to the individual coronary venous system with maximal efficacy and safety in animal studies (11,12).
The aim of this clinical pilot study using selective suction and pressure-regulated retroinfusion for myocardial protection during ischemia in patients undergoing normal risk and high risk PTCA was to assess the efficacy, feasibility and safety of the procedure. Moreover, in a subgroup of patients this new technique of pressure-regulated selective retroinfusion was directly compared with autoperfusion during prolonged balloon inflations.
The study, which was approved by the local ethics committee (University of Munich), included 60 patients with stable angina undergoing PTCA or stent implantation between April 1995 and May 1997 at the Grosshadern University Hospital. All patients gave written informed consent at least 24 h before the procedure.
Forty-five patients with normal risk of PTCA (age 61 ± 11 years) had a leading >75% proximal stenosis of the left anterior descending coronary artery (LAD) without other higher grade stenoses and a normal left ventricular ejection fraction (67 ± 5%). Fifteen patients (age 68 ± 10 years) with high risk of PTCA had either an unprotected main stem stenosis (n = 3) or a main stem equivalent stenosis (n = 12) defined by a leading proximal >75% stenosis of the LAD with a concomitantly documented proximal occlusion of the right coronary artery or left circumflex artery and a history of myocardial infarction in the area of the occluded vessel. In these patients with a moderately decreased left ventricular ejection fraction (mean 51 ± 13%), the area of myocardium supplied by the LAD was estimated to be >40% of the left ventricle and to be of vital importance. In all patients regional myocardial function of the myocardium supplied by the LAD was documented to be normal or only slightly decreased as determined by echocardiography. Patients in whom a four-chamber apical view by echocardiography was not possible in the supine position were not included in the study.
All catheters were inserted through femoral sheaths in the right or left groin. The 7.8F four-lumen retroinfusion catheter (Pro-Med, Austria) was inserted through an 8.5F venous sheath with a side port allowing the delivery of drugs and infusions as required. A 7F left Amplatz II coronary diagnostic catheter (Cordis) was used for catheterization of the orifice of the coronary sinus. After retrograde injection of contrast agent in the coronary sinus (Fig. 1A)to confirm correct placement, a high support coronary guide wire (0.018-in. “Roadrunner,” Cook) was advanced through the coronary sinus into the anterior cardiac vein accompanying the LAD. The retroinfusion catheter was then exchanged using the guide wire in place and advanced until its tip was located in the anterior interventricular vein at the site corresponding to the stenosis of the LAD (Fig. 1, B and C). Without wedging the vein when the catheter balloon was deflated, the correct position of the retroinfusion catheter was confirmed by injection of contrast agent before and at the end of the procedure, documenting also the integrity of the veins. The pressure lumen of the catheter was connected to the system, and coronary venous pressure was continuously monitored.
Coronary angioplasty was performed in the standard manner using a dilation balloon of adequate size. In case of dissection or an insufficient result after balloon angioplasty, stent implantation was performed using a 9- or 18-mm Palmaz-Schatz stent (Johnson & Johnson Interventional Systems) or a 7- or 15-mm PURA stent (Devon, Germany) with subsequent high pressure dilations of 16 to 18 atm (“high energy” noncompliant balloon, Boston Scientific). During the last 9 months of the study, elective stent implantation was performed in all high risk patients (n = 11).
In a subgroup of 10 patients with normal risk of PTCA, after successful stent implantation an autoperfusion balloon catheter (ACS RX Lifestream 3.0 mm, 40 ml/min, Guidant) was used for prolonged (10 min) balloon inflation.
All patients were given aspirin (500 mg) in the morning, and then Rheomacrodex (500 ml) and heparin (10,000 U) after sheath insertion (9F femoral artery, 8.5F femoral vein). In all patients the femoral sheaths were removed 6 h after PTCA or stent implantation. After stent implantation ticlopidin (500 mg/day in two divided doses orally) was started on the same day for 2 months. Aspirin (300 mg) was given for 3 days followed by 100 mg/day.
Selective suction and pressure-regulated retroinfusion
The system for selective suction and pressure-regulated retroinfusion has been described in detail elsewhere (9,10,12). Briefly, the four lumens of the retroinfusion catheter are connected to 1) the high pressure reservoir (2.5 atm), which is filled with arterial blood through the side port of the 9F arterial sheath; 2) the suction pump (−0.9 atm); 3) the pressure sensor of the coronary vein; and 4) the pressure-controlled balloon pump. When electrocardiography triggered (1:2) selective suction and pressure-regulated retroinfusion was activated by the operator, the balloon at the tip of the retroinfusion catheter was first inflated to a pressure of 150 mm Hg. At the same time the suction valve was opened, reducing coronary venous pressure during ischemia (Fig. 2). At 150 to 200 ms before the end of systole the excenter valve for pressure-regulated retroinfusion was opened, allowing retrograde delivery of arterial blood from the high pressure reservoir until the preset coronary venous pressure was reached (Fig. 2). During the retroinfusion period retrograde blood flow was regulated within milliseconds to adjust coronary venous pressure to the preset value. At the end of the pumping period the suction valve was opened again, and this cycle was repeated at the end of the suction period. After retroinfusion during ischemia the balloon was deflated and the pumping line of the retroinfusion catheter was flushed at low flow rates.
After insertion of the retroinfusion catheter, the coronary venous occlusion pressure curve and derived variables (systolic plateau of coronary venous occlusion pressure) were determined by balloon inflation at the tip of the retroinfusion catheter for 30 s before ischemia. Coronary angioplasty was performed with at least two balloon inflations of 60 s in duration in all patients. Retroinfusion was applied during one of the two first balloon inflations in randomized sequence in the patients with normal risk. If additional balloon inflations were necessary, each was supported by retroinfusion but not considered for the analysis of the data from the randomized balloon inflations. In 10 of the patients with normal risk, an additional balloon inflation of 120 s was treated by retroinfusion. In another 10 of the patients with normal risk, selective application of low dose dobutamine (0.1 μg/kg body weight per min), together with retrograde delivery of arterial blood, was performed during an additional balloon inflation using a unidirectional side port between the high pressure reservoir and the retroinfusion catheter. Finally, in an additional group of 10 patients with normal risk, the first balloon inflation of 10 min was treated by retroinfusion; the second balloon inflation of 60 s was not treated; and the third balloon inflation of 10 min was supported by an autoperfusion catheter (ACS RX Lifestream 3.0 mm, 40 ml/min, Guidant).
During retroinfusion, peak and mean coronary venous pressures as well as retrograde blood flow (T106, Transsonic) were determined and the data were stored by the control unit. Between each ischemic period there was at least 3 min of reperfusion. Mean arterial blood pressure, heart rate and a 12-lead electrocardiogram were documented before and at the end of each ischemic period. ST segment changes in the lead showing the greatest deviation from baseline during ischemia without retroinfusion were measured 0.06 s after the J point. Angina score (scale 0 to 10) was evaluated at the end of each balloon inflation.
In high risk patients, all ischemic periods were supported by selective suction and pressure-regulated retroinfusion, except for the last balloon inflation of 60 s, which usually was the high pressure dilation after successful stent placement.
In all patients variables of hemolysis (lactic dehydrogenase, bilirubin, alpha2-haptoglobin) were determined from venous blood samples before and 2 h after PTCA. The hemoglobin concentration was analyzed before and 24 h after the intervention. Clinical follow-up was obtained 3 to 6 months after the intervention.
Regional myocardial function
Regional myocardial function was assessed by echocardiography. For continuous registration of the four-chamber apical view, an adapter (Fig. 1A)was developed, allowing the continuous fixation of the ultrasonic probe (Vingmed GFM 800, Sonotron, Germany) to the chest of the patient. Thus, after baseline recordings the echocardographic window, contrast settings and depth were kept constant during the whole procedure. Echocardiographic images were stored on videotape and processed to an Anchor system (Siemens, Germany) for quantitative analysis by a modified centerline method (13). Twenty-five contiguous chords most affected during ischemia without retroinfusion were used for determination of systolic endocardial movement. The same 25 chords were analyzed for assessment of regional myocardial function before ischemia and during ischemia supported by retroinfusion. The mean value of endocardial movement calculated from the 25 chords at baseline and at the end of the ischemic period was considered for analysis. The same time points were used for semiquantitative echocardiographic analysis (1 = normokinesia; 2 = hypokinesia; 3 = akinesia; 4 = dyskinesia) (14). Thus, each patient was analyzed by two different methods for assessment of regional myocardial function by one operator (centerline method) or by two independent operators (semiquantitative analysis) in a blinded fashion. If the quality of echocardiographic images was judged to be insufficient for quantitative or semiquantitative assessment, these patients were excluded from the echocardiographic analysis.
All data were analyzed with the use of SPSS statistical software. The similarity of baseline values was assessed by the Kruskal-Wallis test. Differences between baseline values and those at the end of the ischemic period with or without retroinfusion or autoperfusion were compared using the Wilcoxon test. The relation between the systolic plateau of coronary venous occlusion pressure determined before ischemia and the preservation of regional myocardial function during ischemia supported by retroinfusion was analyzed by calculation of Pearson’s product-moment correlation coefficient. All data are presented as the mean value ± SD. A p value <0.05 was considered statistically significant.
Feasibility and safety of selective suction and pressure-regulated retroinfusion
Catheterization of the coronary sinus using the femoral approach was successful in 57 (95%) of 60 patients. Access to the coronary sinus was obtained within 3 min in 52 (91%) of 57 patients (Fig. 1A). In the remaining five patients, guiding catheters other than the left Amplatz II were necessary to finally obtain correct placement in the coronary sinus within 10 min. In three patients, however, the guiding catheter could not be placed in the coronary sinus. In all patients with successful catheterization of the coronary sinus, the retroinfusion catheter could be placed in the anterior interventricular vein approximately at the site of the coronary artery stenosis using a high support wire for exchange (Fig. 1B). In five of the first 20 patients who were excluded from further analysis, the retroinfusion catheter became dislocated a few seconds after the start of selective suction and pressure-regulated retroinfusion. After the flexibility of the retroinfusion catheter was reduced in the next series of catheters, no dislocation was observed in the subsequent 37 patients with successful placement of the retroinfusion catheter. Thus, use of selective suction and pressure-regulated retroinfusion was feasible in 52 (87%) of 60 patients who completed the protocol.
No clinical complications (e.g., pericardial effusion, arrhythmias except for premature beats and short salvos [n = 2] during catheterization or vascular complications after femoral sheath removal) related to the retroinfusion procedure were observed. Retrograde injection of contrast agent into the anterior interventricular vein immediately at the end of the intervention did not provide any evidence of damage of the veins or thrombus formation. No hemolysis associated with the retroinfusion procedure was observed. Mean values of alpha2-haptoglobin (1.4 ± 0.5 vs. 1.4 ± 0.5 g/liter), lactic dehydrogenase (213 ± 69 vs. 189 ± 66 U/liter) and bilirubin (0.4 ± 0.3 vs. 0.5 ± 0.3 mg/dl) were similar before and 2 h after the intervention. Mean hemoglobin content decreased from 13.3 ± 1.4 to 12.6 ± 1.8 g/dl, which was probably induced in part by the coronary intervention. Although the arterial blood used for filling of the high pressure reservoir and the retroinfusion system (∼180 ml) was reinfused after the procedure, the retroinfusion procedure might have contributed to the decrease of hemoglobin, because during selective suction and pressure-regulated retroinfusion the sucked venous blood (30 to 100 ml) was not reinfused.
Coronary angioplasty with or without stent implantation was primarily successful in all of these selected patients. No severe hemodynamic alterations (e.g., cardiogenic shock) were observed either in patients with normal risk (n = 37) or high risk (n = 15). None of the patients required emergency coronary artery bypass graft surgery, although seven interventions were performed with surgical standby. Clinical follow-up at 3 to 6 months was uneventful with regard to myocardial infarction or death in all patients, except for one patient who died from cerebral stroke 3 months after the intervention. Repeated coronary revascularization within 6 months after the first intervention was necessary in 9 (17%) of 52 patients for restenosis; 7 patients underwent stent implantation; and 2 patients had elective bypass surgery.
Regional myocardial function
Sufficient quality of echocardiography for analysis of regional myocardial function was obtained by the centerline method in 41 of 52 patients and by semiquantitative determination in 45 of 52 patients, which is comparable to the exclusion rate, owing to poor image quality in similar studies (1,13,14).
Regarding the patients with normal risk and a randomized sequence of treatment, a statistically significant preservation of regional myocardial function in the ischemic area was observed during balloon dilation of 60 s supported by selective suction and pressure-regulated retroinfusion compared with unsupported balloon inflations of the same duration (Fig. 3, Table 1). Quantitative echocardiography showed that ∼76% of baseline regional myocardial function was maintained during balloon inflations supported by retroinfusion, regardless of whether normal risk or high risk patients were analyzed (Fig. 3). Similar data were obtained using the semiquantitative method (Table 1). After prolonged balloon inflation of 120 s supported by selective suction and retroinfusion, regional myocardial function (semiquantitative analysis) was preserved at the same level as that after 60 s of ischemia in 10 patients (apical septum: baseline 1.1 ± 0.3; 60 s of ischemia 1.9 ± 0.6; 120 s of ischemia 2.1 ± 0.6). In the patients treated with the addition of low dose dobutamine to the retrogradely infused arterial blood, similar results of regional myocardial function were obtained as in the patients who did not receive dobutamine.
In an additional group of 10 patients with normal risk, retroinfusion was directly compared with autoperfusion during two balloon inflations of 10 min duration. Both retroinfusion and autoperfusion improved regional myocardial function compared with control occlusions of 60 s (Fig. 4). This preservation of regional myocardial function after 60 s of ischemia was not statistically different after 10 min of ischemia supported by retroinfusion or autoperfusion (Fig. 4). However, regional myocardial function tended to be lower with autoperfusion than during retroinfusion (Fig. 4). Four patients showed a decrease in mean blood pressure <70 mm Hg after 10 min of autoperfusion (Fig. 4)and a concomitant decrease in regional myocardial function to <30% of baseline. In the same patients retroinfusion was able to preserve regional myocardial function after 10 min of ischemia at 60% to 70% of baseline (p < 0.05).
St segment changes and angina score
In the patients with a randomized sequence of treatment, the magnitude of ST segment changes was lower during balloon inflations supported by retroinfusion (0.16 ± 0.12 mV) compared with balloon inflation retroinfusion (0.24 ± 0.16 mV, p < 0.05) of the same duration (60 s). Angina occurred in 55% of the unsupported balloon inflations and in 33% of supported balloon inflations, with the angina severity score in supported balloon inflations (1.6 ± 1.9) comparing favorably to unsupported balloon inflations (3.5 ± 2.3, p < 0.05).
When all patients with randomized treatment were considered, mean arterial blood pressure decreased to 89% of baseline after 60 s of ischemia not supported by retroinfusion and to 81% of baseline in high risk patients (Table 2). Values obtained after 60 s of ischemia supported by selective suction and retroinfusion (96% of baseline in all patients, 91% in high risk patients) (Table 2)compared favorably to unsupported ischemia (p < 0.05). In 12 patients showing a drop in systolic blood pressure <90 mm Hg during unsupported balloon inflations within 33 ± 12 s, retroinfusion was able to maintain blood pressure >90 mm Hg in all of these patients during 60 s of ischemia.
With the addition of low dose dobutamine to the retrogradely infused arterial blood in 10 patients, no change in mean arterial blood pressure was observed after 60 and 120 s of ischemia (Table 2). Heart rate did not change during ischemia supported by retroinfusion with arterial blood and low dose dobutamine. There was also no difference in heart rate between supported and unsupported balloon inflations after 60 s of ischemia (Table 2).
In patients with direct comparison of retroinfusion with autoperfusion, both techniques were able to preserve mean arterial blood pressure in patients (n = 4) showing a decrease in mean arterial blood pressure <70 mm Hg during unsupported balloon inflation after 60 s of ischemia (Fig. 4). After 10 min of ischemia, mean arterial blood pressure was maintained at the same level as that after 60 s only during retroinfusion (Fig. 4).
Coronary venous pressure and retrograde flow rates
The systolic plateau of the coronary venous pressure occlusion curve determined before ischemia ranged between 20 and 79 mm Hg (mean 53 ± 12). The adjustable retroinfusion pressure during ischemia was chosen to be 20 mm Hg higher than the systolic coronary occlusion pressure in each patient. However, the preset pressure level was reached in only 22 of 52 patients by selective pressure-regulated retroinfusion. Thus, considering all patients, peak coronary venous pressures were increased from 21 ± 6 mm Hg before ischemia to 53 ± 19 mm Hg during ischemia supported by retroinfusion (p < 0.05). Mean coronary venous pressure during the retroinfusion periods was increased from 12 ± 5 mm Hg before ischemia to 35 ± 15 mm Hg during ischemia (p < 0.05). The peak retrograde flow rate was 105 ± 22 ml/min (mean 40 ± 13). There was no difference in coronary venous pressures or retrograde flow rates during retroinfusion between normal risk and high risk patients.
Although the preset retroinfusion pressure was not reached in all patients, a linear relation (r = 0.73, p = 0.002) between individual systolic plateau of coronary venous occlusion pressure determined before ischemia and preservation of regional myocardial function (percent baseline, centerline method) during ischemia supported by retroinfusion was observed, which is in agreement with experimental data (11).
To our knowledge, this single-center pilot study is the first to apply selective suction and pressure-regulated retroinfusion clinically in 52 patients who underwent normal risk or high risk balloon angioplasty or stent implantation. The newly developed system, which was extensively studied in animals previously (9,12)and also compared to previous systems of unselective retroperfusion (9), offers a unique approach to the selective application of retroinfusion of arterial blood and drugs to the ischemic myocardium without affecting nonischemic myocardium (12). Because of the pressure regulation of the device, retroinfusion flow can be adapted to the individual venous system during each retroinfusion period to obtain maximal efficacy, avoiding unnecessary high peak and mean coronary venous pressures at the same time (Fig. 2).
The main finding of the present studywas that use of selective suction and pressure-regulated retroinfusion is safe and highly efficient in preserving regional myocardial function of the ischemic myocardium during normal risk and during high risk PTCA. The addition of low dose dobutamine to the retrogradely pumped arterial blood during selective suction and pressure-regulated retroinfusion of the anterior interventricular vein (12)was able to further stabilize hemodynamic variables during the coronary intervention without undesired systemic effects.
Feasibility, safety and efficacy
An overall high success rate of 95% was observed for correct placement of the retroinfusion catheter in the anterior interventricular vein at the corresponding site of the proximal stenosis of the LAD. In contrast to previous studies (1,2,4,15), the femoral approach (16)was used for the catheterization of the coronary sinus and final placement of the retroinfusion catheter in the anterior interventricular vein.
In this first clinical study the protocol of selective suction and pressure-regulated retroinfusion was completed in only 87% of patients, owing to dislocation of the retroinfusion catheter during treatment in five patients. However, this does not appear to be a major limitation of the method, because after stabilization of the body of the retroinfusion catheter, no further dislocations were observed in the last 37 patients. No complications related to the application of selective suction and pressure-regulated retroinfusion occurred, and the system was safe at least during short-term treatment (10 min). Although in the present study peak and mean coronary venous pressures were higher than those reported in previous retroperfusion studies (1,2), there was no evidence of coronary venous damage. Thus, selective suction and pressure-regulated retroinfusion to achieve systolic coronary venous occlusion pressures obtained before ischemia (mean 51 mm Hg) do not appear to be associated with a higher risk of damage to the coronary venous system or ischemic myocardium (17).
Although the preset coronary venous pressures during retroinfusion were not reached in all patients, owing to the limited retrograde transcatheter blood flow of the initial device, preservation of regional myocardial function at ∼75% of baseline during supported ischemia indicated that this retroinfusion device was highly efficient (Fig. 3). The quantitative results of echocardiography were confirmed by blinded semiquantitative analysis (Table 1). The reduction of ischemia leading to preservation of regional myocardial function during retroinfusion-supported balloon inflations was consistent with the reduction of ST segment changes as well as semiquantitative angina score. Although alternate balloon dilations in randomized sequence were compared in the patients with normal risk, myocardial preconditioning might have influenced the results. However, brief periods of myocardial ischemia, as used in this study, did not show preconditioning effects on regional myocardial function or ST segment changes during balloon angioplasty in humans (18). From all variables used for assessment of regional myocardial protection during retroinfusion, we infer that ischemia was not completely prevented in all patients with the limited retrograde flow rates of the retroinfusion catheters used in this study. Important findings, however, were that similar efficacy to preserve regional myocardial function was obtained in high risk patients and that during prolonged balloon inflations up to 10 min this effect of retroinfusion was maintained (Fig. 4).
The observed effects of selective suction and pressure-regulated retroinfusion on regional myocardial function were associated with a stabilization of hemodynamic variables during ischemia, although a slight decrease in mean arterial blood pressure was not completely prevented in normal risk and high risk patients (Table 2). It was a consistent finding in the small group of patients supported by retroinfusion and selective application of low dose dobutamine, however, that mean arterial blood pressure remained unchanged even if ischemia was prolonged to 120 s. Because we did not observe any undesired systemic effects (e.g., heart rate did not change) or regional effects using selective dobutamine administration in combination with arterial retroinfusion, it seems to be a promising approach, particularly in high risk patients.
Comparison of retroinfusion with autoperfusion
Direct comparison of retroinfusion with autoperfusion in the same patients showed that retroinfusion had at least the same efficacy as autoperfusion during 10 min of ischemia. When using autoperfusion catheters with an estimated anterograde flow rate of 40 ml/min at a normal blood pressure in this study, higher mean retrograde flow rates of 59 ml/min were necessary to obtain similar efficacy during pressure-regulated retroinfusion, which is in agreement with experimental data (12,19). The well known reduction of autoperfusion flow with decreasing blood pressure resulted in a substantial decrease of regional myocardial function after 10 min of ischemia in 4 of 10 patients (Fig. 4). In the same patients, however, pressure-regulated retroinfusion was able to maintain regional myocardial function and mean arterial blood pressure (Fig. 4), indicating that retroinfusion was less dependent than autoperfusion on blood pressure in preserving regional myocardial function.
Whether the stabilization of regional myocardial function and hemodynamic variables by selective suction and pressure-regulated retroinfusion observed during 10 min of ischemia is maintained during longer periods of ischemia in case of “bail-out” situations remains to be demonstrated because none of these situations occurred in the present study.
Limitations of retroinfusion support during high risk coronary interventions
Although stent implantation has reduced the incidence of unmanageable “bail-out” situations and increased the safety of high risk coronary interventions (20–24), there are still a number of advantages that might be offered by an efficient regional support device such as selective suction and pressure-regulated retroinfusion in high risk patients. Preventing myocardial ischemia and hemodynamic alterations in high risk patients may help to correctly place and extend a stent without the otherwise imminent risk of the patient rapidly developing cardiogenic shock during coronary occlusion. The same benefit should be offered by the support device in case of “bail-out” situations with interruption of blood flow, where it is difficult or even not possible to place a stent. In this situation, it is an important advantage of the retroinfusion support device compared with autoperfusion (25)or anterograde transcatheter perfusion (26)that the stenting procedure is still possible and not hampered by the application of the support device. Finally, if the “bail-out” situation cannot be resolved, a continued regional support against myocardial ischemia using retroinfusion should be able to at least prevent the development of myocardial infarction (1,10).
The concept of preventing severe ischemia and hemodynamic alterations by selective suction and pressure-regulated retroinfusion in patients with high risk coronary interventions in combination with stent placement was associated with a high primary success rate and an excellent clinical outcome in this first clinical study. These preliminary data, however, from a small group of selected high risk patients, do not allow us to decide whether the high success rate was due to the application of retroinfusion or to stent placement. Furthermore, in this study only patients with proximal LAD stenoses were supported by retroinfusion of the anterior ventricular vein. In the meantime, selective retroinfusion of the left marginal vein has been successfully performed in three patients with a leading stenosis of a large first marginal branch, which was the only vessel supplying the remaining myocardium in these patients (data not shown). For support of the circumflex region, the selectivity of retroinfusion must be reduced by placing the catheter tip in the proximal great cardiac vein. Retroinfusion of the region of the right coronary artery, however, is certainly limited by the variable anatomy, and thus unpredictable access to the veins draining the region of the right coronary artery.
A major limitation of retroinfusion support during myocardial ischemia is its limited efficacy in case of circulatory standstill. Although the system of selective suction and pressure-regulated retroinfusion may operate in an untriggered mode and might prevent myocardial infarction, hemodynamic support is not provided during circulatory standstill. Hence, selective suction and pressure-regulated retroinfusion might prevent regional ischemia and the development of cardiogenic shock in high risk patients. However, other support devices such as the cardiopulmonary bypass (7)or the hemopump (27,28)have to be considered in the rare but difficult situation of circulatory standstill without immediate successful resuscitation.
Whether selective suction and pressure-regulated retroinfusion can fulfill the criteria described earlier for a feasible and efficient support device and whether it is cost effective during high risk coronary interventions and in case of “bail-out” situations is being now studied in a recently initiated multicenter trial.
☆ This study was supported by Grant Bo 991/1-4 from the Deutsche Forschungsgemeinschaft, Bonn, Germany.
- left anterior descending coronary artery
- percutaneous transluminal coronary angioplasty
- Received October 30, 1997.
- Revision received February 6, 1998.
- Accepted February 18, 1998.
- by the American College of Cardiology
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