Peter T. Mortensen

The Pacing Therapies for Congestive Heart Failure (PATH-CHF) Study: Rationale, Design, and Endpoints of a Prospective Randomized Multicenter Study

In conjunction with pharmacologic therapy, pacing has been proposed as a potential treatment to decrease symptoms in patients with moderate-to-severe congestive heart failure (CHF). Uncontrolled studies of pacing therapy for CHF dealing with different pacing sites, modes of pacing, and atrioventricular delays have reported mixed outcomes. The Pacing Therapies in Congestive Heart Failure (PATH-CHF) study is a single-blind, randomized, crossover, controlled trial designed to evaluate the effects of pacing on acute hemodynamic function and to assess chronic clinical benefit in patients with moderate-to-severe CHF. The effect of pacing on oxygen consumption at peak exercise and at anaerobic threshold during cardiopulmonary exercise tests, and on 6-minute walk distance, have been selected as primary endpoints of the study. Secondary endpoints of the trial were changes in New York Heart Association (NYHA) functional class, quality-of-life as assessed by the Minnesota Living with Heart Failure questionnaire, and hospitalization frequency. Finally, changes in ejection fraction, cardiac output, and filling pattern were assessed by echocardiography. The trial was planned to include 53 patients from 7 centers in Europe over a period of 3 years. The study was divided into 2 parts: acute testing and chronic follow-up. The acute study, performed during the pacemaker implantation, involved extensive testing using a custom-designed computer (FLEXSTIM) and a unique burst pacing protocol (FLEXSTIM protocol) to determine the best ventricular pacing sites and the most appropriate atrioventricular delays. The chronic phase consisted of a crossover study designed to test in each patient the best univentricular pacing site and biventricular pacing as assessed by the acute hemodynamic study. The study started with the first implant in 1995 and has, to date, included 42 patients. The study is expected to be completed by the end of 1998. The results of a first interim analysis showed trends toward improvement in all primary and secondary endpoints during the pacing periods compared with no pacing.

Sequential Biventricular Pacing

The study evaluated the clinical safety, performance, and efficacy of sequential biventricular pacing in the InSync III (Model 8042) biventricular stimulator in a multicenter, prospective 3‐month study and assessed the proper functioning of features aiming at improving biventricular AV therapy delivery. The system was successfully implanted in 189 (95.9%) of 198 patients with symptomatic systolic heart failure and a prolonged QRS complex duration. Patients significantly improved their 6‐minute hall walk distance (baseline 339 ± 92 vs 3‐month 422 ± 127 meter, P < 0.001) and NYHA class (baseline 3.1 ± 0.5 vs 3‐month 1.9 ± 0.7, P < 0.001). Echocardiographic optimization of sequential biventricular pacing showed an improvement in stroke volume compared to simultaneous stimulation (sequential 68 ± 24 mL vs simultaneous 56 ± 23 mL, P < 0.001) at baseline and at 3 months. In 88% (30/34) of the patients these improvements were seen within a small range of V‐V delays of ±20 ms and in 94% (32/34) within V‐V delays of ±40 ms. In contrast, programming beyond this range reduced stroke volume below that during simultaneous biventricular pacing. The device functioned as expected. LV lead dislodgement was observed in 12 patients and phrenic nerve stimulation required lead repositioning in 2 patients. Eight patients died during the study. Patient survival at 3 and 6 months was 97 ± 2% and 94 ± 2%, respectively. Cause of death was cardiac (n = 7), heart failure related (n = 3), arrhythmia related (n = 2), and unknown (n = 2). In conclusion, this sequential biventricular pacemaker was safe and efficacious. (PACE 2004; 27:339–345)

The superior transseptal surgical approach to mitral valve creates slow conduction.

Background: Atrial tachycardia is very frequent after mitral valve surgery using the superior transseptal approach.