Hemodynamic effects of left ventricular pacing site in an animal model of heart failure

Aims: Missing response to left ventricular (LV) pacing is observed in 20–30% of heart failure (HF) patients, possibly the ideal pacing site was not reached by the coronary sinus lead. This study investigates how different epicardial and endocardial pacing sites influence hemodynamic performance in an animal model.

Methods: In six adult sheep dilated HF was induced by rapid pacing. Endocardial mapping and pacing were performed using a 64-electrode basket catheter. Epicardial pacing was achieved by temporary electrodes. LV volumes and diameters were measured by Echocardiography.

Results: Table 1 summarizes the hemodynamic and echocardiographic results.

LVDd: diastolic LV diameter IVSd: interventricular septum diameter; *(p<0.05) **(p>0.05)
	Baseline	Lateral Wall	Inferior Wall	Apex	RV	Lateral Wall	Inferior Wall	Apex	RV
		ENDOCARDIAL				EPICARDIAL
Heart Rate*	82.8 ±10.2	102.0 ±4.5	102.0 ±4.5	99.8 ±7.4	97.2 ±1.9	103, ±6.7	102.0 ±4.5	100.0 ±0.0	96.2 ±5.8
RR mean*	73.0 ±17.7	82.2 ±13.2	65.0 ±16.7	64.0 ±18.4	58.8 ±11.6	83.0 ±16.1	66.2 ±15.8	67.6 ±10.2	56.4 ±12.4
PAP mean**	18.8 ±6.9	19.6 ±11.9	18.4 ±8.1	18.8 ±8.9	17.0 ±5.4	18.4 ±5.4	18.2 ±3.9	19.6 ±5.1	19.2 ±4.3
PC WP*	12.4 ±5.5	10.8 ±3.6	14.0 ±3.5	14.8 ±3.5	15.6 ±4.1	10.6 ±3.4	15.6 ±2.8	15.2 ±3.2	14.8 ±3.3
CO*	2.7 ±0.4	3.8 ±0.6	2.8 ±0.6	2.7 ±1.1	2.0 ±0.9	3.6 ±0.6	2.7 ±0.4	2.5 ±0.7	2.1 ±0.5
LVDd*	4.87 ±0.7	4.06 ±0.8	5.25 ±0.2	5.16 ±0.6	5.91 ±0.2	4.55 ±0.4	5.83 ±0.6	5.16 ±0.7	5.67 ±0.4
IVSs	1.40 ±0.2	1.85 ±0.1	0.99 ±0.2	1.28 ±0.2	0.64 ±0.4	1.79 ±0.2	0.99 ±0.3	1.11 ±0.1	0.67 ±0.3

Conclusion: In this sheep model with induced HF, endocardial and epicardial pacing of the lateral myocardium led to optimal systolic function and hemodynamics, right ventricular pacing induced further reduction of LV performance. As this optimal pacing site cannot always be reached via the coronary sinus, surgical implantation of epicardial electrodes should be considered in all nonresponding patients.