Influence of Cardiac Resynchronization Therapy on Cardiac Structural and Electrical Remodeling

Introduction: Cardiac resynchronization therapy(CRT) has proven effective in patients with EF < 35%, wide QRS, and advanced heart failure. We sought to determine the extent of change for measures of intracardiac conduction over time and how these measures relate to structural and clinical variables. Methods: Data was collected from 30 pts. who were enrolled in the Boston Scientific DECREASE-HF trial. NYHA class and measures of intracardiac conduction; intrinsic AV and V-V delays, QRS duration, and AV delay during AAI pacing were collected at baseline and at 3 mth intervals. Echocardiographic measures of left ventricular end-systolic(LVESV) and end-diastolic(LVEDV) volumes were collected at baseline, 3 and 6 mths. The data was analyzed using paired t-tests and linear regression models, adjusting for repeated measures within each patient. Results: LVESV was significantly reduced at 6 mths. NYHA improved at least 1 class in 57% and 63% of pts. at 6 mths and final visit. Within the overall group there were no significant changes in any measures of intracardiac conduction between the baseline and 6 mth visit or the last visit (Table 1) but changes were observed in individual patients. Both LVEDV and LVESV were significantly associated with AV delay (p<.01 for both, effect size: -.23ms change in AV for a 1 ml decrease in LVEDV, -.22ms for LVESV). Conclusions: In these patients, CRT induced structural and clinical improvements. While there was no overall average difference in intracardiac conduction intervals, individual patient change and fluctuation from visit to visit was observed.

Table 1.

	Value	Baseline	6 mths (n)	Final Visit	Change@6mths (n)	p-value	Change@Final Visit	p-value
	LVESV (ml)	138 ± 51	120 ± 52 (26)	N/A	-21 ± 34 (26)	0.005	N/A	N/A
	LVEDV (ml)	196 ± 57	188 ± 65 (26)	N/A	-9 ± 36 (26)	0.192	N/A	N/A
	Intrinsic AV (ms)	201 ± 44	199 ± 46 (27)	200 ± 42	0 ± 27 (27)	1.000	-1 ± 35	0.837
	AAI-AV (ms)	279 ± 49	273 ± (26)	273 ± 41	4 ± 23 (26)	0.409	-6 ± 33	0.301
	Intrinsic QRS (ms)	173 ± 21	170 ± 20 (27)	176 ± 24	-1 ± 21 (27)	0.725	3 ± 22	0.455
	Intrinsic V-V (ms)	75 ± 46	73 ± 48 (27)	78 ± 41	-0.2 ± 14 (27)	0.939	3 ± 20	0.413

(n=30 unless noted){reported values:mean± sd}[Final visit 29mths 14-33].