JACC: Surgical CRT helps patients with unfavorable coronary sinuses
For patients with unfavorable coronary sinus (CS) vein anatomy, cardiac resynchronization therapy (CRT) via a surgical minithoracotomic approach is preferable to transvenous lead implantation, according to a study published in the July 26 issue of the Journal of the American College of Cardiology. However, an accompanying editorial recommended caution when deciding whether to recommend routine CT scans to define anatomy in possible CRT candidates due to iatrogenic radiation exposure.

“CRT efficacy depends on proper positioning of the LV [left ventricular] lead over the posterolateral wall. A detailed pre-operative knowledge of CS [coronary sinuses] anatomy might be of pivotal importance to accomplish a proper LV lead placement over this area,” wrote Francesco Giraldi, MD, of the Centro Cardiologico Monzino, Istituto di Ricerca e Cura a Carattere Scientifico in Milan, Italy, and colleagues.

During the study, Giraldi et al evaluated 40 heart failure patients with an indication to CRT and unsuitable coronary sinus branches to compare the clinical, echocardiographic exercise testing response to CRT in patients with unfavorable anatomy of the CS veins.

Patients were randomized to receive either transvenous or surgical left ventricular (LV) lead implantation and had a mean age of 66 years. During the study, 20 patients underwent surgical minithoracotomic LV lead implantation and 20 patients were implanted transvenously.

The authors evaluated NYHA functional class, echocardiographic and cardiopulmonary exercise testing data before and one year after CRT system implant.

In patients who underwent surgical minithoracotomic LV lead implantation, LV leads were placed over the middle-basal segments of the posterolateral wall of the LV. The researchers reported a significant improvement of NYHA functional class, LV ejection fraction (from 28.8 percent to 33.9 percent), LV end-systolic volume (165 ml to 134 ml) and peak Vo2/kg (10.4 ml/kg/min to 13.1 ml/kg/min) in the patients who underwent surgical minithoracotomic LV lead implantation. However, patients who were implanted transvenously saw no improvements in left ventricular ejection fraction (LVEF), LV end-systolic volume or peak VO2/kg.

Changes after CRT between groups were highly significant. Additionally, the authors reported that 12 months after implantation, during a multivariate analysis in surgical patients, the improvements of NYHA class, LVEF, peak VO2 and peak VO2/kg were significantly higher than in nonsurgical patients. After 12 months of CRT, the heart failure-related hospitalizations for each patient were significantly lower in the group of patients who underwent surgical minithoracotomic LV lead implantation compared to those who did not.

“Finally, after CRT procedure in transvenous and surgical patients, the use of beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, loop and potassium-sparing diuretics, nitrates and digoxin was optimized by the HF specialist, without significant differences between the two groups’ patients,” the researchers wrote.

The authors concluded that in patients with unfavorable CS anatomy, surgical strategies at a selective lead positioning over the middle-basal segments of the lateral of the middle area of posterolateral wall of the LV are superior to transvenous placement in a second- or third-choice segment guided by local anatomy.

In the current study, dyssynchrony and nonposterolateral lead position was associated with an inadequate LV reverse remodeling response. The authors found that the rate of responders to CRT increased from 60 percent in the presence of dyssynchrony alone to 86 percent when dyssynchrony and posterolateral LV lead position coexisted.

In an accompanying editorial, Kenneth A. Ellenbogen, MD, and Jordana Kron, MD, of the Virginia Commonwealth University Medical Center in Richmond, said that Giraldi et al’s study set out to examine an important clinical question: “How should an electrophysiologist treat a heart failure patient who needs CRT but has challenging CS anatomy?” However, Ellenbogen and Kron offered that the answer relies on gaining a deeper understanding about electrical and mechanical dyssynchrony.

Researchers said that a limitation of the study is the small patient population. A larger, more prolonged study should be undertaken to confirm the findings and before a large-scale utilization of surgical LV lead positioning can be proposed in patients with unfavorable cardiac veins anatomy.

“Data from this study underline the importance of the pre-operative knowledge, gained in the present study by MSCT [multi-scanner CT], of CS main branches anatomy, because it allows the screening of patients with unfavorable anatomic patterns,” the authors concluded. “The improvement of clinical, echocardiographic and CPET [cardiac PET] parameters recorded in surgical patients as compared in patients in whom the lead was placed into another nonposterolateral vein, suggests that physicians should consider the epicardial implantation as the first line approach in patients with unfavorable CS anatomy.”

While Ellenbogen and Kron offered that the study did find that “LV lead location does matter,” at least in some patients, they said unknowns remain, including whether LV lead position should be dictated by electrical latency or mechanical latency.

Ellenbogen and Kron said physicians should exhibit caution before recommending routine CT scans to define anatomy in patients who are candidates for CRT due to the potential for patients to experience iatrogenic radiation exposure, especially because fluoroscopy times during CRT can be prolonged.

“We are just beginning to understand the complexity of LV activation in heart failure patients and in patients with biventricular pacing. While we await the results of future trials, we do not feel a change in clinical practice is warranted based on the current state of knowledge, and we do not endorse pre-procedural CT scans because of concern about increased radiation exposure,” Ellenbogen and Kron concluded.