Myocardial protection in the failing heart: I. Effect of cardioplegia and the beating state under simulated left ventricular restoration

Abstract

Coronary blood flow alterations occurred only in failing hearts when geometry was changed from closed to open state. The beating method provided more endocardial flow than cardioplegic delivery during ventricular exposure for restoration. Vascular remodeling raised coronary vascular resistance in failing hearts, thereby requiring higher pressure for similar blood flows.

Remodeling of left circumflex coronary arterial tree in pacing-induced heart failure

“…Helmer et al (6) indicated that the LV free wall received less blood flow with an increased flow resistance than the septum during 21-28 days of ventricular pacing. We found that the 3-to 4-wk ventricular pacing increased the vascular flow resistance by ϳ100% in an open heart procedure in situ perfused by nonpulsatile cardioplegia (16,18). The ex vivo measurements indicated ϳ75% increase in vascular flow resistance of the LV free wall (i.e., 1.2 Ϯ 0.11 mmHg·min·ml Ϫ1 in control vs. 2.1 Ϯ 0.15 mmHg·min·ml Ϫ1 in CHF, while the computational results were within Ϯ1 SD of the measurements), which was less than the in situ change likely because of the substantial lack of vasomotor tone in the ex vivo measurement.…”

“…The chest was closed, and the animal was allowed to recover from the surgery for 1 wk. Ventricular pacing was then initiated at 210 -220 beats/min for 1 wk, and 190 -220 beats/min for additional 2-3 wk, depending on the status of the heart (16,18).…”

“…Numerous studies have examined the ventricular function, stroke volume, myocardial blood flow, cellular and extracellular structural changes within the myocardium, contractile processes in isolated myocytes, levels of catecholamines, activation of the ␤-adrenergic receptor system, and neurohormonal system in the pacing-induced CHF (6, 20, 22-24, 26, 31, 35, 36, 38, 40, 41). The increase of vascular flow resistance and the regional deficit of myocardial blood flow were also found after the LV pacing (6,16,18,24). There are no systematic studies on the structure-function remodeling of the entire coronary arterial tree in response to the increase of vascular resistance in the pacing-induced CHF.…”

Surgical Treatment for Heart Failure

“…Vascular remodeling raises the coronary vascular resistance in the failing heart, thereby requiring higher pressure for similar blood flow. 16 For the SAVE operation under a beating heart, the LV is opened from the apex to the base along to the left anterior descending artery. Although kinesis of the LV wall is examined preoperatively, palpation of the LV muscle during its contraction allows differentiation of akinetic and normal muscle.…”

“…After the SAVE operation, 16 the conical shape is restored by inserting an oblique patch between the apex and high septum, just below the aortic valve, with subsequent closure of the excluded wall over the patch. It has been proposed that successful surgical LV restoration should restore normal helical myofiber orientation.…”