Author + information
- Andrew D.M. Grant, MD,
- Nicholas G. Smedira, MD,
- Randall C. Starling, MD, MPH and
- Thomas H. Marwick, MD, PhD, MPH⁎ ()
- ↵⁎Cardiovascular Medicine J1-5, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, Ohio 44195
We appreciate the interest of Dr. Thomas and colleagues in our work (1).
Our goal was not so much to produce a new score, but to propose strain as a guide for the assessment of right ventricular (RV) function. Evaluating the RV in these circumstances seems like a rational step: the recognition of severe RV dysfunction might reasonably lead the clinician to opt for a biventricular device in the first instance. However, evaluation of the RV remains challenging, and our observation is that strain, as a geometry-independent technique, avoids the limitations of the typical RV measures. Perhaps because of this, it is more predictive of RV failure than standard measures. However, as an ejection-phase marker, strain is load dependent: in this population, the correlation between RV strain and afterload (mean pulmonary artery pressure, r = 0.16) was greater than that with pre-load (right atrial pressure, r = 0.03). Given the elevation of both of these markers in almost all patients, it is possible that the responses of RV strain to manipulations in pre-load, afterload, or contractility would add additional predictive value, but we did not test this.
There were 3 barriers to the study of elective biventricular devices. First, insufficient numbers were available to address this question, which probably requires a multicenter study to obtain sufficient numbers of patients. Second, most of these patients were on extracorporeal membrane oxygenation, which has a major influence on attempted RV function measurement. Third, a study design to show the value of RV evaluation is difficult in patients with biventricular devices; certainly, the chosen endpoint has no meaning in these patients.
The multiplicity of prognostic scores in the ventricular assist device literature is perhaps a reflection of the fact that some episodes of RV failure are due to bleeding, RV ischemia, and accidental mechanical damage to the RV, as Dr. Jorde et al. propose. These are unpredictable events that compromise the performance of any score. Notwithstanding the role of unpredictable contributors, RV strain seems to be a useful factor when considering the possible contributors to RV dysfunction in this population.
- 2013 American College of Cardiology Foundation