Mechanical and electrical causes for lack of frequency potentiation in normal patients, in coronary artery disease and in left bundle branch block.
Nine atrial pacing (SP) runs and 8 ventricular pacing (VP) runs were carried out in patients without heart disease, and 10 AP runs in patients with coronary artery disease (CAD). For evaluation of myocardial contractility, the time derivative of left ventricular pressure (dpdt) was used. Comparing rest and AP at 155/min, AP in normal patients revealed a significant increase in dP/dtmax and a significant decrease in left ventricular end-diastolic pressure (LVEDP). This represents frequency potentiation. When comparing rest and VP values at 155/min in normal patients, no changes in dP/dtmax and LVEDP were seen. AP in patients with CAD demonstrated no change in dP/dtmax, but a decrease in LVEDP when compared to the rest values. dP/dtmin and left ventricular systolic pressure did not change in the 3 groups. VP, and even AP, in 2 additional patients with isolated left bundle branch block (LBBB) AND WITHOUt associated heart disease, revealed the same constellation of parameters as VP in normal patients. Our results show a lack of frequency potentiation in normal patients during VP and in patients with isolated LBBB during both AP and VP. It is concluded that the lack of frequency potentiation during AP in CAD is produced primarily by mechanical asynchrony of contraction, angiographically demonstrated as akinesia and dyskinesia. The lack of frequency potentiation in normal patients during VP and in patients with isolated LBBB due to asynchrony of activation resulting in asynchrony of contraction.
D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D002037:Bundle-Branch Block / Q000209:etiology / Q000503:physiopathology*; D014695:Cerebral Ventriculography; D003327:Coronary Disease / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006329:Heart Conduction System; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D011199:Potentiometry