The present study validates that smaller surface (i.e., 1.5 mm2) steroid-eluting electrode designs offer excellent pacing and sensing performance with significantly higher pacing impedances. Although questions remain as to the cause of late exit block in two patients in this series, this relatively small surface electrode design offers promise toward achieving greater pacing efficiency and a theoretical 13%-16% (minimum) enhancement in permanent pacemaker longevity.

Diastolic pressure-length relationships of an ischemic region of the canine left ventricle were measured over a six-hour period following left anterior descending coronary artery ligation, and their evolution was compared with the extent of systolic aneurysmal bulging. Normalized ischemic segment length excursion, which after coronary artery ligation may be taken as a measure of systolic aneurysmal bulging, increased during the first hour after ligation but thereafter declined toward control values. Concurrently, reciprocal changes were demonstrated in the slope of the end-diastolic pressure-length curves obtained during transient pressure loading of the left ventricle. These data show that the magnitude of acute systolic aneurysmal bulging followed experimental coronary artery ligation is determined not only by loss of contractile function, but also by changes in passive pressure-length relationships of the myocardium. Moreover, the results indicate that development of akinesis in experimental ischemia, heretofore demonstrated only in the chronic phase of infarction, may begin within hours of the onset of myocardial ischemia.

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Figure 1 depicts two rhythm strips obtained shortly after implantation of a Biotronikf active fixation electrode {IVE-185) in an 83-year-old man in whom the establishment of effective stable pacing had proven to be a major clinical challenge. He had presented with recurrent syncopal spells secondary to intermittent high grade atrioventricular block manifested by a slow ventricular response to chronic atrial fibrillation. His underlying heart disease was a cardiomyopathy with massive ventricular dilitation and biventricular failure. It was assumed he had markedly flattened trabeculae in the dilated right ventricle due to the inability to successfully place the standard passive fixation electrode on three prior attempts. He was deemed too ill to tolerate even a limited thoracotomy for placement of epicardial electrodes and a fourth procedure was undertaken using the Irnich electrode. The biotronik bayonet connector was subsequently cut off and a standard terminal pin spliced on to fit the patient's pulse generator which was a nonprogrammable model set at a pacing interval of 840 ms. Shortly thereafter the Address for reprints: Dr, Levine.

No abstract