High-frequency QRS potentials as a marker of myocardial dysfunction after cardiac surgery.
BACKGROUND
High-frequency QRS potentials are sensitive to myocardial ischemia. The aim of this study was to evaluate the usefulness of high-frequency QRS potentials as a marker of myocardial dysfunction after cardiac surgery.


METHODS
Seventy patients undergoing coronary artery bypass grafting or heart valve surgery were involved. High-frequency QRS potentials were measured by signal-averaged electrocardiogram, and calculated as the root-mean-square voltage of the total QRS duration (RMST). The postoperative RMST was expressed as a percentage of the preoperative RMST. The mean RMST at 1 to 2 hours after removing the aortic cross-clamp was compared with the cardiac index, inotropic agents, and aortic cross-clamping time. The occurrence of ventricular tachycardia within 24 hours and the RMST at 2 postoperative days were also evaluated. Patients were divided into quartile groups from highest to lowest at postoperative RMST (groups 1, 2, 3, and 4, respectively, from maximum to minimum).


RESULTS
In postoperative states, cardiac index significantly decreased in accordance with the RMST decrease in a stepwise manner, although there were no differences in cardiac index among the four groups preoperatively. Inotropic agents and aortic cross-clamping time increased as RMST decreased. A high rate of ventricular tachycardia within 24 hours and delayed RMST recovery at 2 postoperative days were seen in group 4. The curve of sensitivity and specificity showed that severe reduction (threshold, 35%) of RMST indicated low-output syndrome.


CONCLUSIONS
The severe reduction of filtered high-frequency QRS potentials was related to myocardial dysfunction. Measurement of filtered high-frequency QRS potentials could become a useful, noninvasive, real-time monitor of myocardial dysfunction after surgery.
Matsushita
Shonosuke
S
Department of Surgery, University of Tsukuba, Institute of Clinical Medicine, Tsukuba, Japan. shomatsu@md.tsukuba.ac.jp
Sakakibara
Yuzuru
Y
Imazuru
Tomohiro
T
Noma
Mio
M
Hiramatsu
Yuji
Y
Shigeta
Osamu
O
Jikuya
Tomoaki
T
Mitsui
Toshio
T
D002303:Cardiac Output, Low / Q000175:diagnosis* / Q000188:drug therapy / Q000209:etiology; D002316:Cardiotonic Agents / Q000627:therapeutic use; D001026:Coronary Artery Bypass; D004562:Electrocardiography; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000209:etiology
D002316:Cardiotonic Agents