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Division of Cardiovascular and Thoracic Surgery, St. Lukes/Roosevelt Hospital, 1111 Amsterdam Ave, New York, NY 10025
(Email: dswistel{at}chpnet.org).
For the last 10 years, cardiac resynchronization therapy (CRT) has emerged as an increasingly important therapeutic option in the management of heart failure, especially in light of stagnating numbers of available donor hearts and the ever enlarging number of individuals who would benefit from transplantation. Furthermore, proven improvement in clinical symptoms, hemodynamics, and quality of life have all been shown in nontransplant candidates. The authors in the preceding article [1] analyze the results of CRT on a large series of transplant candidates for an average period of 3 years. Their results are similar to our own [2], which show dramatic improvement in survival compared with historic controls, consisting of patients with similar New York Heart Association (NYHA) functional classification. The limitation of the study is the lack of randomization, but about 90% of the studied group was in the NYHA class III or IV, and approximately 90% had a left ventricular ejection fraction of less than 20%, and as the authors correctly point out, considering the severity of disease and the CRT guidelines, such a randomization would be unethical. The data confirms the significant long-term benefit of CRT in heart failure patients.
An important finding that the authors also confirm is a nonresponder rate of approximately 20% to 30%, which is similar to other published reports. No mention is made of the mode of implant of the left ventricular lead, whether transvenous or epicardial, in this article. In patients in which transvenous lead implantation is either impossible or suboptimal, we have justified a rationale for the use of the posterior approach for epicardial lead placement (with the use of a robotic system), because of improved left ventricular response rates with directed lead placement [3]. In this series, the average ejection fraction was 13%, and the nonresponder rate was only 14%.
An important distinction is made between patients who suffer from dilated cardiomyopathy (DCM) versus coronary heart disease (CHD). The latter suffer from a much higher rate of nonresponders, presumably due to the hearts' inability to remodel secondary to transmural scarring from ischemia. Although the authors state that none of these patients required coronary revascularization, we have often found that this distinction is made on the basis of negative nuclear scan, in which obstructive pathology is considered nonbypassable, not because there is no obstruction, but because the scan does not confirm ischemia. We have found that the use of dobutamine stress echocardiography to determine inotropic contractile reserve, very accurately predicts the degree of reverse remodeling, and those that would benefit from coronary revascularization plus CRT, rather than CRT alone [4].
The authors point out a useful scheme for the triage of patients awaiting transplant. Those individuals who do not show improvement in functional measurements should be listed for transplant, but if while waiting on the list, functional improvement occurs, they can be ultimately de-listed, because the long-term survival with just CRT in these patients is better than with transplant.
Last, the authors point out that a significant percentage of patients with atrial fibrillation will revert to sinus rhythm after some degree of remodeling takes place after CRT. This is of great interest, as the need for atrioventricular (AV) node ablation can be reduced with its resultant need for unphysiologic right ventricular stimulation.
I commend the authors on their analysis of such a large group of patients with CRT and their excellent results. This confirmation of functional improvement over a relatively long time should stimulate the more widespread acceptance of this procedure. Furthermore, the knowledge that a significant number of patients in heart failure with atrial fibrillation will remodel after CRT and revert to sinus rhythm should save a number of individuals from unnecessary AV node ablation.
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