TRANSCUTANEOUS CARDIAC PACING DURING THORACIC-SURGERY - FEASIBILITY AND HEMODYNAMIC EVALUATION BY TRANSESOPHAGEAL ECHOCARDIOGRAPHY

Background. Occasionally, emergency perioperative pacing is necessary. Transcutaneous cardiac pacing is noninvasive, safe, and readily avail able. Its feasibility and hemodynamic effects during thoracic surgery and one-lung ventilation have not been established. Methods: Twenty an esthetized patients (aged 25-70 yr) without cardiac disease undergoing elective pulmonary resection (right n = 10, left n = 10) were studied in normal sinus rhythm and during transcutaneous cardiac pacing. Pati ents were paced in supine and lateral decubitus positions (with closed and opened chest) at the minimal current necessary to produce ventric ular capture. Invasive arterial monitoring permitted calculation of me an arterial pressure, and transesophegeal echocardiography was used to assess atrial and ventricular wall motion and the evaluation of trans mitral flow. Twelve patients underwent Doppler analysis of pulmonary v enous flow. Results: Pacing was achieved in atl patients, with a mean threshold of 86.9 +/- 20.6 mA for the right thoracotomy group, and 106 .7 +/- 16.2 mA for the left thoracotomy group. The mean paced heart ra tes for the right and left thoracotomy groups were 101.6 +/- 18.2 and 105.4 +/- 11.5 beats/min, respectively. During pacing, all patients su stained reversible transient decrements in mean arterial pressure (9-1 9%) from baseline, the loss of AV synchrony, and the development of pa radoxical ventricular septal wall motion. No patient had significant m itral regurgitation during sinus or paced rhythms. Decreased systolic pulmonary venous flow velocity and abnormal systolic flow reversal wer e seen during pacing in 11 of the 12 patients studied. Conclusions: Tr anscutaneous cardiac pacing is effective in patients undergoing thorac otomy and one-lung ventilation. Its use in patients in normal sinus rh ythm induces reversible decrements in mean arterial pressure because o f the effects of altered atrioventricular association, ventricular wal l motion, and pulmonary venous return.