Non-invasive Evaluation of Ventricular Function and Volumes During Atrioventricular Sequential and Ventricular Pacing LUIS R. ROMERO, CHARLES L HAFFAJEE, WILLIAM LEVIN, PAUL W. DOHERTY, BAROUH V. BERKOVITS, and JOSEPH S. ALPERT With the technical assistance of RICHARD SERINO and JAMES MURPHY From the Division of Cardiovascular Medicine, Department of Medicine, and the Department of Nuclear Medicine, University of Massachusetts Medical School, Worcester, Massachusetts ROMERO, L. R., ET AL.: Non-invasive evaluation of ventricular function and volumes during atrio- ventricular sequential and ventricular pacing. Thirteen patienfs who ail had previously inserted tem- porary or permanent pacemakers [6, VVJ; 7, A-V sequential) were studied by two-diniensionaJ echocar- diography and radionuclide gated blood pool ventricuiography (RVG) for non-invasive evaluation of cardiac performance. Patients were paced in both the VVl mode and during sinus/atriai or A-V sequential pacing. Although there was no objective change of the ejection fraction during V-pacing and atrial/A- V sequential pacing or sinus rhythm, as has been previously reported, A-V sequential pacing did resuit in significant improvement in overall cardiac/unclion and output as judged by radionuclide ventric- uiography and blood pressure response in most of our patients. An appropriately timed atriaJ contribulion to ventricular systole resulted in improved ventricular function in those individuals with pre-existing systolic or diastoiic myocardioi dys/unction and/or sick sinus syndrome in whom pacemaker therapy was indicated. Hadionuclide venlricuiogruphy appears to be a reJiabJe, accurate, non-invasive method that can be used to evaluate patients before implanfafion of a permanent ventricular or atrioventricuiar pacemaker in order to decide which pacing mode is best for thai particular individual. (PACE. Vol. 7, January-February, 1984] radionuciide veniriculography, ventricular pacing. A-V sequentiaJ pacing, cardiac /unction The physiologic significance of the atrial con- traction and its relationship to ventricular func- tion was carefully documented in 1911 by Gessel et al.' Thereafter, a number of cardiovascular phys- iologists studied the effects of atrial transport on ventricular function in both animal models"' and human beings.''^ Following the studies of Wiggers and his colleagues, establishing the reaction of mammalian myocardial muscle to artificial elec- trical stimuli, external electrical pacing of the heart emerged as a possible therapeutic modality for a variety of cardiac diseases."^ Address for reprints: C. I. Haffajee, M.D.. Division of t^lardio- vascular Medicine. University of Mas.sac;husetts Medical Cen- ter, 55 Lake Avenue Nortli. Worcesler, MA 016U5. Received September 21. 1982; revision received November 10, 1982: accepted November 11. 1982. The importance of an appropriately timed atrial contraction for optimal ventricular performance during ventricular systole has been evaluated dur- ing normal sinus rhythm, and artificial pacing in dogs and humans.^''^ These studies documented that well-timed atrial transport"^ leads to aug- mented ventricular diastolic volume, thereby shifting ventricular filling upward on the Frank- Starling curve.'° An inappropriately short atrio- ventricular time delaymay fail to produce adequate ventricular filling with resultant diminution in stroke volume.'* Conversely, an excessively long atrioventricular time delay may result in de- creased cardiac output secondary to late mitral valve closure with resultant "atriogenic" mitral regurgitation." '^ During junctional or ventricular rhythms (naturally occurring or ventricularly paced), the absence of adequate preload may cause 10 lanuary-February 1984 PACE. Vol. 7