A new method for the placement of epicardial atrial-pacing electrodes

Temporary epicardial atrial pacing electrodes: duration of effectiveness based on position

BACKGROUND

To investigate the duration of effectiveness in the postoperative period of temporary epicardial atrial pacing electrodes on the right atrium, based on position.

METHODS

The function of temporary epicardial atrial pacing electrodes were examined in 55 patients undergoing coronary artery bypass grafting from March 20, 1996, to July 31, 1996, at Allegheny University Hospitals, Hahnemann Division, Philadelphia, PA. There were 41 male and 14 female patients. The mean age was 71 years (range 35 to 86 years). Two atrial and two ventricular temporary epicardial pacing electrodes were placed at the termination of cardiopulmonary bypass. One atrial electrode was placed on the body of the right atrium at the junction of the superior vena cava (body electrode); the other was passed through the pursestring of the atrial cannulation site (appendage electrode).

RESULTS

The mean thresholds for the atrial body electrodes on the operative day and postoperative days 1 and 2 were 4.96, 6.67, and 6.80 mA, respectively. The mean thresholds for the atrial appendage electrodes were 5.98, 7.50, and 8.59 mA, respectively.

CONCLUSIONS

Temporary epicardial atrial pacing electrodes are more effective when the wires are placed in the atrial body of the right atrium than if they are wrapped within the pursestring of the right atrial appendage. As a result of these findings, the common practice of placing the pacing wire through pursestring tissue should be abandoned.

Continuous rapid atrial pacing to control recurrent or sustained supraventricular tachycardias following open heart surgery

A technique is described to control recurrent or sustained supraventricular tachycardia associated with rapid ventricular rates following open heart surgery. The technique utilizes a pair of temporarily implanted atrial epicardial wire electrodes to pace the heart. In one group of patients with recurrent atrial flutter and 2:1 A-V conduction, continuous rapid atrial pacing at 450 beats/min produced and sustained atrial fibrillation. The ventricular response rate immediately slowed when compared to that during atrial flutter, and if further slowing was required, it was easily accomplished by the administration of digitalis. Another group of patients with different arrhythmias (recurrent paroxysmal atrial tachycardia, sustained ectopic atrial tachycardia, or sinus rhythm with premature atrial beats which precipitated runs of atrial fibrillation) was treated with continuous rapid atrial pacing to produce 2:1 A-V block. In all instances, the continuous rapid atrial pacing suppressed the supraventricular tachycardia and maintained the ventricular response rate in a therapeutically desirable range. It was demonstrated that the technique is safe, effective, and reliable.

Atrial and ventricular pacing after open heart surgery

The effect of cardiac pacing, through a wide range of pacing rates, has been studied in 13 patients in stable sinus rhythm within 24 hours of operation. Using first atrial and then ventricular pacing, the cardiac rate was raised to 60% above control value. The effects of atrial and ventricular pacing were compared by observing the differences in the various parameters measured at corresponding paced heart rates. With atrial pacing there was no significant difference in the cardiac output, mean aortic pressure, mean left atrial pressure, or left ventricular work. During ventricular pacing there were significant falls in cardiac output (p<0·05), mean aortic pressure (p<0·01), and left ventricular work (p<0·01). There was a significant rise in mean left atrial pressure (p<0·01).

In this study atrial pacing had no significant effect on the parameters measured, through a wide range of cardiac rates. An inotropic effect resulting from increase of rate was not seen. Reported increases in cardiac output following pacing must therefore have resulted from correction of a dysrhythmia. Ventricular pacing incurs a definite haemodynamic penalty if used in patients with an intact atrioventricular conducting pathway. If atrial pacing is not available, this penalty must be balanced against the possible haemodynamic advantage of suppressing a dysrhythmia.

Hemodynamic evaluation of rate augmentation produced by atrial pacing and isoproterenol in the early postoperative phase of cardiac valve surgery

The hemodynamic effects of atrial pacing were evaluated in a group of 19 patients soon after cardiac valve surgery. Atrial pacing at 30 beats/min above the control rate of 88 beats/min produced an increase in cardiac index of 600 ml/min/m 2 .

Isoproterenol was infused into eight of these patients to produce an increment in heart rate identical to that during atrial pacing. In these patients atrial pacing produced an increment in cardiac index of 400 ml/min/m 2 as compared to an increment of 1400 ml/min/m 2 produced by isoproterenol.

It is concluded (1) that atrial pacing is a useful technique for augmenting cardiac index soon after cardiac valve surgery and (2) that isoproterenol provides a greater increment in cardiac index at identical heart rates and the major portion of its effect is directly inotropic.

Aortic valve surgery as an emergency procedure

Twenty-three patients critically ill from aortic valvular disease underwent emergency aortic valve replacement as a life-saving measure. Sixteen patients (70%) survived hospitalization and 14 (61%) are presently living. Of eighteen patients who underwent solitary aortic valve replacement, there were four hospital deaths and two late deaths. Five patients required double valve surgery, with three hospital deaths and no late deaths. The survivors often had dramatic improvement and have done well during an average follow-up period of 9 months. The major factor contributing to mortality after surgery was irreversible myocardial damage particularly evident in patients with longstanding severe valvular disease. Valve replacement can be successfully accomplished in patients critically ill with aortic valve disease, especially if it occurs as an isolated lesion.