Left Ventricular Mechanics and Myocardial Blood Flow: Coronary Flow and CFR

Left Ventricular Mechanics and Myocardial Blood Flow: Coronary Flow and CFROur results are relevant to those of Nelson et al, who found that cardiac resynchronization in patients with dilated cardiomyopathy and left bundle branch block improved LV contractile function with a modest decline in oxygen utilization.
We also speculate that the restoration of a normal LV activation sequence in our patients does not affect intrinsic myocyte function but rather provides its net effect by the enhancement of the effectiveness of the work performed by different regions of the LV wall, which performed dyssynchronous contraction during right apical ventricular stimulation. read more
In this study, we found that, in patients receiving long-term DDD pacing, the resting flow in the dominant coronary artery increases significantly immediately after the restoration of a normal ventricular activation sequence. This finding is in agreement with that of Nielsen et al, who used 13-N-labeled ammonia positron emission tomography scanning for myocardial blood flow quantification. We also found that the CFR in the same artery is reduced significantly during the change of pacing mode to AAI.
Previous studies have shown that, in patients receiving long-term pacing through the right ventricular apex, both the baseline coronary blood flow and the coronary flow during maximal hyperemia are impaired in comparison with healthy control subjects. These findings have been attributed to changes in the regulation of coronary flow due to functional and/or structural abnormalities induced by permanent ventricular pacing.
According to our findings, the restoration of a normal activation sequence improves baseline coronary flow significantly in the dominant coronary artery but does not affect coronary flow during maximal hyperemia. The above findings are probably due to the fact that the restoration of a normal ventricular activation sequence blunts functional abnormalities in the short term but has a small effect or no effect on the structural abnormalities induced by permanent right ventricular apical pacing.

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