Irreversible ischemic injury occurs after coronary artery occlusion in vivo, first in the subendocardium and progressing toward the subepicardium over time. presumably due to transmural variations in collateral flow or wall tension. In this study, 10 left ventricular globally ischemic slabs were created that were free of wall tension and collateral flow. The onset and completion of ischemic con...

82 Myocardial infarction (MI) may be associated with abnormal Q waves associated with the typical progression of ST segment elevation myocardial infarction (STEMI) and T wave inversions described in Chapter 8. In many cases, however, myocardial ischemia (with or without actual infarction) may be limited primarily to the subendocardium (inner layer) of the ventricle, often associated with ST seg...

Lipomas of the heart are encapsulated tumors that are composed primarily of mature fat cells. Cardiac lipomas can originate either from subendocardium (approximately 50%), subpericardium (25%), or from the myocardium (25%) and may be located more frequently in left ventricle or right atrium. We report a 74-year-old female who presented with dyspnea on exertion and was found to have 5×5 cm mass ...

BACKGROUND To determine the mechanisms of ventricular tachycardia (VT) in humans, three-dimensional intraoperative mapping of up to 156 intramural sites was performed in 13 patients with healed myocardial infarction and refractory VT. METHODS AND RESULTS Mapping was of sufficient density to define the mechanism of 10 VTs in eight patients. In five of 10 cases, sustained VT was initiated in th...

BACKGROUND In Langendorff-perfused hearts and in hearts on cardiopulmonary bypass, chemical ablation of the subendocardium of both ventricles decreases ventricular vulnerability to fibrillation. It was hypothesized that the effects of ablation are a result of the elimination of the subendocardial Purkinje fiber network. This hypothesis has been supported by recent observations that the supernor...

BACKGROUND Experimental hypercholesterolemia (HC) impairs intramyocardial microvascular function. However, whether this is associated with alterations in microvascular architecture remained unknown. Using a novel 3D micro-CT scanner, we tested the hypothesis that HC is associated with an alteration in the microvascular architecture. METHODS AND RESULTS Pigs were euthanized after 12 weeks of e...

BACKGROUND Defibrillation may be improved if electrode configurations can be found that create a larger and more even voltage gradient field across the heart. This study determined the magnitude of the shock gradient fields generated by four nonthoracotomy electrode configurations for defibrillation. METHODS AND RESULTS In six dogs, a catheter was inserted containing a right ventricular apica...

The present study was undertaken to characterize regional myocardial alterations of reflected ultrasound during the cardiac cycle in normal, ischemic, and postischemic reperfused myocardium. Time-averaged integrated backscatter (IB) and cardiac cycle-dependent amplitude modulation were measured from subepicardial, midmyocardial, and subendocardial regions of the left ventricular apex and the mi...

AIMS On the basis of an MRI study it has been suggested that subendocardial hypoperfusion is present in patients with cardiac syndrome X. However, further work is required to test whether these findings can be generalized. METHODS AND RESULTS MRI was used to visually and semi-quantitatively assess subendocardial and subepicardial perfusion, at rest and during an infusion of adenosine, in 20 p...

Myocardial ischemia is transmurally heterogeneous where the subendocardium is at higher risk. Stenosis induces reduced perfusion pressure, blood flow redistribution away from the subendocardium, and consequent subendocardial vulnerability. We propose that the flow redistribution stems from the higher compliance of the subendocardial vasculature. This new paradigm was tested using network flow s...