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Biomedical subjects

J D Slack

Publications and source records attributed to J D Slack.

64 records · Page 4Linked to original sources
PubMed1981

Limitations of postextrasystolic potentiation in identifying ischemic myocardium.

To evaluate the usefulness of postextrasystolic potentiation in differentiating ischemic yet viable myocardium from infarcted myocardium, 20 dogs were chronically instrumented with left ventricular pressure gauges, left circumflex coronary artery flow probes, occluders, pacing wires, and ultrasonic segment-length transducers. Ten dogs had acute (1 h) coronary occlusions followed by reperfusion (4 days) and were then killed. Ten more dogs had more prolonged (1 mo) occlusions and were then killed. Timed premature ventricular contractions were induced, and the postextrasystolic beat was evaluated. In ischemic segments that were hypokinetic, postextrasystolic potentiation of shortening occurred in both groups. In ischemic segments that were akinetic or dyskinetic, potentiation of shortening did not occur in either group. Both groups showed recovery of shortening, and histologically normal myocardium was identified in the region between the segments in all animals. Thus, akinetic and dyskinetic segments did not show postextrasystolic potentiation of shortening, even though the tissue was viable and showed functional recovery. Failure to improve shortening after a premature ventricular beta in an ischemic segment does not necessarily indicate nonviable myocardium.

Action Potentials↗
PubMed1981

Prinzmetal's angina: atypical angiographic features of atypical angina pectoris.

Clinicians have puzzled over the coronary physiology associated with atypical angina pectoris for the past century. Recent recognition of coronary artery spasm, which has been so thoroughly documented with coronary angiography, has resolved many of these conceptual difficulties. However, several features of coronary artery spasm, both spontaneous and secondary to provocation with ergonovine maleate, remain poorly understood. This paper addresses the management problems associated with spontaneously occurring spasm in the setting of pre-existent atherosclerotic coronary artery disease, angiographically severe spasm unassociated with symptoms of angina pectoris or signs of myocardial ischemia, and the precipitation of angina pectoris by ergonovine maleate administration unaccompanied by demonstrable epicardial coronary artery spasm. The rationale, indications and therapeutic efficacy of a new class of agents known as slow channel inhibitors of calcium antagonists are discussed.

Acute Disease↗
PubMed1980

Limitations of post-extrasystolic potentiation in assessing regional myocardial viability in man.

UNLABELLED: To investigate the usefulness of regional response to post-extrasystolic potentiation as a predictor of left ventricular viability in patients with coronary artery disease, 46 patients underwent calibrated biplane left ventricular cineangiography during which a single, timed ventricular premature contraction was introduced. RESULTS: Of 758 normal or hypokinetic segments, 486 (64.1%) showed a positive response to post-extrasystolic potentiation. Of 116 akinetic or dyskinetic segments, only 51 (43.9%) showed a positive response to post-extrasystolic potentiation (P less than 0.001). Because akinetic or dyskinetic areas would not be expected to respond to post-extrasystolic potentiation based on animal laboratory data, alternative explanations were sought to explain such positive response in man. Analysis of percent change in chord length of normal or hypokinetic segments adjacent to akinetic or dyskinetic segments that did or did not respond to post-extrasystolic potentiation revealed (10.2% +/- 1.2%) vs (1.3% +/- 0.7%) improvement, respectively (P less than 0.001) (mean +/- SE). CONCLUSION: Passive rather than active events may be responsible for "improved" regional wall motion following post-extrasystolic potentiation in akinetic or dyskinetic regions. If unrecognized, these factors may lead to improper interpretation of "intervention ventriculography" utilizing post-extrasystolic potentiation.

Angiocardiography↗
PubMed1980

Recurrent sustained ventricular tachycardia: report of a case with His-bundle branches reentry as the mechanism.

A 57-yr-old man with coronary artery disease presented with recurrent sustained ventricular tachycardia. During electrophysiologic study, the following observations suggested His-bundle branches (His-BB) reentry as the underlying mechanism of ventricular tachycardia: (1) the initiation of ventricular tachycardia by a premature ventricular beat was related to the presence of retrograde His--Purkinje conduction (V2H2) delay; (2) the QRS configuration of tachycardia complexes was similar to that of V1 and V2; (3) each QRS complex of tachycardia was consistently preceded by a His bundle deflection with an H-V interval which was equal to or longer than that of sinus beats; (4) atrioventricular dissociation was present during tachycardia; and (5) after procainamide a greater V2H2 delay was required to initiate the tachycardia. The therapeutic implications of identifying and differentiating the His-BB (macro) reentry from micro reentry are discussed.

Bundle of His↗
PubMedDate not supplied

Complex coronary angioplasty: use of extended and angled balloon catheters.

Certain anatomical features of coronary artery stenoses are recognized to be associated with a high risk of acute closure during percutaneous transluminal coronary angioplasty. Balloon catheters with extended balloon lengths were developed and tested in nonsegmental stenoses and multiple stenoses in series. Balloon catheters with acute angulation were also designed and tested in stenoses located in tortuous, angulated arterial segments. Clinical experience with these unique balloon configurations is presented.

Angioplasty, Balloon↗
PubMedDate not supplied

Percutaneous transluminal angioplasty involving internal mammary artery bypass grafts: a femoral approach.

Percutaneous transluminal coronary angioplasty is an effective technique for the treatment of selected patients with ischemic heart disease due to coronary artery stenosis. Successful angioplasty in saphenous vein bypass grafts has been documented, but little experience has been reported using angioplasty in internal mammary artery to coronary artery bypass grafts. Nine of ten patients with stenosis in the internal mammary artery to coronary artery anastomosis or in the coronary vessel distal to the anastomosis site were successfully treated with angioplasty. One patient developed restenosis 1 month after the procedure, and a repeat angioplasty was successful. In one patient, the balloon catheter could not be advanced through the left internal mammary artery to the stenosis site. Technical features of internal mammary artery angioplasty are discussed, including the use of specially designed guiding wires, guiding catheters, and balloon catheters that facilitate angioplasty involving internal mammary arteries from the femoral approach.

Angioplasty, Balloon↗
PubMedDate not supplied

A regional ultrasonic technique to measure left ventricular performance during coronary artery bypass.

Miniaturized, highly accurate pressure transducers and segment length measuring devices have been proven a safe, practical and stable method of analyzing cardiac performance in both acute and chronic animal experimentation. We have utilized a micromanometer-tipped intraventricular catheter and an ultrasonic segment length gauge implanted in the subendocardial layer of the left ventricle at the time of cardiac surgery to measure changes in systolic function and diastolic compliance prior to and after the completion of the operative procedure in man. No complications of this technique were encountered in the thirty patients studied. Continuous improvements in instrument design, data collection and data processing suggest future clinical applications are possible and desirable.

Compliance↗