Author + information
- Philip B. Dattilo, MD⁎ (, )
- Anand Prasad, MD,
- Emily Honeycutt, MBI,
- Tracy Y. Wang, MD, MHS, MSc and
- John C. Messenger, MD
- ↵⁎Division of Cardiology, University of Colorado School of Medicine, MS B-130, 12601 East 17th Avenue, Aurora, Colorado 80045
- fractional flow reserve
- intermediate coronary stenosis
- intravascular ultrasound
- percutaneous coronary intervention
To the Editor:
The use of fractional flow reserve (FFR) and intravascular ultrasound (IVUS) to assess intermediate coronary stenoses (defined as 40% to 70% stenosis) has been associated with improved procedural and clinical outcomes (1,2) in patients undergoing percutaneous coronary intervention (PCI). Both technologies received a Class IIa recommendation for use in angiographically intermediate coronary stenoses in the recently published 2011 American College of Cardiology/American Hospital Association PCI guidelines (3). We undertook an analysis of the CathPCI Registry data in order to better understand current patterns of use of both FFR and IVUS associated with PCI of intermediate lesions, and how their use might relate to procedural and patient-based outcomes.
The CathPCI Registry is an initiative of the American College of Cardiology Foundation and the Society for Cardiovascular Angiography and Interventions and has been previously described (4). We analyzed data for patients undergoing PCI of intermediate coronary stenoses (defined as a percent diameter stenosis ≥40% and ≤70%). Patients were excluded if PCI was performed for a nonintermediate stenosis (n = 373,320), if they underwent diagnostic angiography only (n = 1,977), or if they underwent both FFR and IVUS (n = 778). We examined data starting from April 2009 when version 4 of the CathPCI Registry data collection form began to be implemented, as IVUS and FFR use for PCI of intermediate stenoses were not collected in earlier versions.
Descriptive statistics on the study population were grouped by lesion assessment (angiography only [AO], FFR, or IVUS). Categorical variables were presented as percentages, and continuous variables were presented as medians along with the interquartile range (IQR). Comparisons between groups were performed using Pearson chi-square tests for categorical variables and the Kruskal-Wallis test or Wilcoxon test for continuous variables. Logistic regression with generalized estimating equations to account for within hospital clustering was used to compare in-hospital mortality and procedural success adjusting for baseline patient characteristics in the CathPCI Registry mortality risk model. All analyses were performed using SAS version 9.2 (SAS Institute, Cary, North Carolina).
Data for 61,874 attempted coronary interventions of intermediate coronary stenoses performed between April 2009 and September 2010 were available for analysis. Among these, FFR was used in 3,763 (6.1%) patients, IVUS was used in 12,589 (20.3%) patients, and 45,522 (73.6%) patients had lesions assessed by AO (Table 1). Compared with patients who underwent AO, patients undergoing FFR were more likely to be younger (p < 0.0001) and more frequently male (p < 0.0001), with slightly lower rates of diabetes (p = 0.017) and hypertension (p = 0.0003), and higher rates of dyslipidemia (p < 0.0001). Patients undergoing IVUS were younger (p < 0.0001) and less frequently male (p < 0.0001), with slightly lower rates of diabetes (p < 0.0001) and similar rates of hypertension (p = 0.75) and dyslipidemia (p = 0.31).
Patients undergoing FFR were more likely to have had their procedure performed in a university hospital (p < 0.0001) compared with private and community hospitals (p < 0.0001) and in a hospital with a fellowship or residency training program (p < 0.0001).
Patients who underwent FFR were less likely to present with an acute coronary syndrome (ST-segment elevation myocardial infarction, non–ST-segment elevation myocardial infarction, and unstable angina; p < 0.0001). Patients who underwent IVUS were more likely to undergo stress testing prior to the procedure (p < 0.0001). Patients undergoing FFR were more likely to have had a prior stress test that had negative or equivocal findings (p < 0.0001).
Patients undergoing FFR and/or IVUS were less likely to have multivessel disease (p < 0.0001), and more likely to have a lesion deemed high risk (p < 0.0001). Both the FFR and IVUS cohorts had longer fluoroscopy times (p < 0.0001) and more contrast use (p < 0.0001) as compared with the AO group.
After adjusting for comorbid conditions, the use of IVUS was associated with higher rates of major bleeding (odds ratio [OR]: 1.23; IQR: 1.09 to 1.38; p < 0.001), lower rates of in-hospital death (OR: 0.66; IQR: 0.44 to 0.98; p = 0.04), and no difference in procedural success (OR: 1.10; IQR: 0.97 to 1.26; p = 0.14) compared with AO. No difference between the FFR and AO groups was seen in adjusted comparisons of mortality (OR: 1.07; IQR: 0.53 to 2.15; p = 0.857), major bleeding (OR: 0.95; IQR: 0.76 to 1.19; p = 0.683), or procedural success (OR: 0.97; IQR: 0.76 to 1.25; p = 0.836).
This analysis demonstrates that despite a wealth of data demonstrating the utility of these technologies in the evaluation of intermediate coronary stenoses (1,2), IVUS (20.3%) and FFR (6.1%) are used in only a small minority of such cases. The use of IVUS was likely more common than FFR due to its demonstrated utility in determining appropriate stent sizing, as well as the post-implantation evaluation of stent expansion and apposition. A number of factors probably contributed to these low rates of use, such as the fact that the catheters used to perform these lesion assessments are costly and are poorly reimbursed, if at all. In fact, routine use may provide a financial disincentive, as the cost of the procedure increases with the use of the catheters and the reimbursement decreases with less frequent stent implantation.
After adjustment for comorbidities, IVUS appears to be associated with lower rates of in-patient mortality, a finding consistent with prior data (5). It was also associated with higher rates of major bleeding, whereas FFR showed no such correlations. Neither technology was associated with differences in procedural success.
We were unable to explicitly examine cases where either of these technologies was used to deem a lesion physiologically insignificant and PCI was deferred, as these cases are not captured in the CathPCI Registry dataset. The CathPCI Registry dataset only records outcomes occurring in the hospital stay during which PCI was performed. Given that these data were analyzed retrospectively, outcomes associated with the use of IVUS and FFR are observational and causality cannot be inferred.
Please note Dr. Wang has received research grants to the Duke Clinical Research Institute (<$10,000) from Bristol-Myers Squibb/Sanofi Partnership, Schering Plough/Merck, The Medicines Company, Heartscape, Canyon Pharmaceuticals, and Eli Lilly/Daiichi Sankyo Alliance; and consulting/honoraria (<$10,000) from The Medicines Company and AstraZeneca. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. This research was supported by the American College of Cardiology Foundation's National Cardiovascular Data Registry (NCDR).
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