Postextrasystolic potentiation during spontaneous ventricular ectopy in man. Associated left ventricular volume changes determined by list mode radionuclide ventriculography.

Five patients with spontaneously arising frequent ventricular ectopia were studied by list mode radionuclide ventriculography. Changes in left ventricular volumes reflected the increased inotropy of the postextrasystolic sinus beats: stroke volume increased by +36.0 +/- 32.8% (P less than 0.05) and end-systolic volumes decreasing by 13.6 +/- 7.3% (P less than 0.02) leading to an increased ejection fraction (+31.1 +/- 23.8%; P less than 0.05). There were no significant increases in end-diastolic volumes (+2.2 +/- 5.4%; P:NS). The reproducibility of the left ventricular volume estimates was confirmed by comparing the control sinus beats with the interrupted sinus beats. There were no significant changes in end-diastolic (+1.8 +/- 5.5%), end-systolic (+1.8 +/- 3.7%) and stroke volumes (+5.4 +/- 14.6%). List mode radionuclide ventriculography can be used to accurately monitor left ventricular volume changes associated with spontaneously arising ventricular ectopia. In these patients, the contribution of Frank-Starling mechanism to postextrasystolic potentiation was minimal.