Jayne Alison Morris-Thurgood

Septal short atrioventricular delay pacing: additional hemodynamic improvements in heart failure.

Controversy exists as to whether short AV delay pacing is beneficial in left ventricular dysfunction with the studies performed coming to disparate conclusions. The right ventricular apical pacing previously studied results in asynchronous contraction and relaxation sequences and may limit the potential benefits of short AV delay pacing. In this study the hemodynamic effects of septal (resulting in a more physiological activation sequence) and apical right ventricular activation were compared in 15 patients with heart failure. VDD pacing with AV delays of 50,100, and 150 msec was evaluated. Apical VDD pacing did not increase the cardiac output significantly, 4.1 ± 0.75 to 4.45 ± 0.74 L/min, whereas septal VDD pacing increased the cardiac output to 4.86 ± 0.79 L/min (P = 0.037). Apical pacing increased the cardiac output in 10 patients and septal pacing in 11 patients. We conclude that selected patients with ventricular dysfunction benefit from short AV delay pacing. Septal ventricular activation confers significant hemodynamic improvements over apical activation.

Are we being driven to two sensors?: clinical benefits of sensor cross-checking.

Sensor cross‐checking within dual sensor rale responsive pacemakers is designed to reduce the incidence of inappropriate rate response. We describe a patient in whom sensor cross‐checking prevented the occurrence of angina during automotive transport.

Hemodynamic and metabolic effects of paced linkage following heterotopic cardiac transplantation.

BACKGROUND AND PURPOSE Heterotopic cardiac transplantation is a valuable surgical technique that maximizes the use of donor organs. However, recipient heart function may decline steadily postoperatively with resulting clinical deterioration. Paced linkage has the potential of reducing afterload and enhancing coronary flow of both hearts, thereby improving recipient- and donor-heart function. This may have long-term as well as short-term benefits. METHODS AND RESULTS The study was performed on 11 heterotopic transplant recipients. The two hearts were linked with a pacemaker (paced linkage) to produce recipient heart systole during different periods of donor-heart diastole. The recipient ventricular contraction was timed to occur during early, mid, and late diastole of the donor heart. Hemodynamic baseline measurements were compared with the optimal counterpulsated data. Paced linkage produced significant improvements in total cardiac output, 5.0 +/- 0.9 compared with baseline 4.5 +/- 0.8 L/min (P = .021); recipient coronary sinus flow, 278 +/- 145 versus 186 +/- 108 mL/min (P = .022); and aortic systolic pressure, 135 +/- 27 versus 123 +/- 27 mm Hg (P = .005). There was an overall improvement in systolic ventricular performance in the recipient heart when pace linked, as evidenced by a significant increase in left ventricular systolic pressure of 118 +/- 36 compared with the baseline value of 108 +/- 33 mm Hg (P = .016), an increase in ejection period from 174 +/- 30 versus 203 +/- 48 (P = .046), and a decrease in the pre-ejection period of 147 +/- 37 when paced versus 181 +/- 39 milliseconds (P = .013). The metabolic studies showed a significant decrease in hypoxanthine release from a baseline level of 0.4 mumol/L to a paced value of -0.06 mumol/L (P = .002); these very low values would suggest that there is no evidence of ischemia. Hemodynamic changes in the donor heart included a significant reduction in the left ventricular end-diastolic pressure from 6.8 +/- 4.4 versus baseline of 10.5 +/- 5.8 mm Hg (P = .029) and in maximum -dP/dT from 3.2 +/- 1.7 versus baseline of 2.1 +/- 1.1. CONCLUSIONS Paced linkage after heterotopic cardiac transplant produces significant functional improvements in both hearts. Permanent pacemaker implantation may sustain these acute benefits and prevent the premature deterioration of the recipient heart.

Effects of paced counterpulsation on exercise capacity and hemodynamics after heterotopic heart transplantation.

Abstract This study shows that improvements in resting hemodynamics translate to a small but significant improvement in exercise duration. At our institution we are now implanting pacemakers as early as possible in the postoperative period and are investigating the influence of long-term pacing on recipient left ventricular function and quality of life.

Respiratory-dependent pacing: a dual response from a single sensor.

Five patients with respiratory dependent rate responsive pacemakers (Biorate HDP3, Biotec) were studied using ambulatory telemetry to evaluate the sensitivity of this pacing system to nonrespiratory signals. In each case the pacemaker was implanted in the left infraclavicular position with an impedance sensing electrode inserted into the subcutaneous tissues of the anterior chest wall. The pacing rate was 73 ± 2 beats per minute at rest and rose by 42 ± 5 beats per minute when the patients were walking with both arms swinging (mean ± SEMJ. Three of the five patients had sensing electrodes that extended across the midline. In this subgoup, pacing rate rose by 26 ±4 beats per minute when walking with arms held immobile and by 36 ± 2 beats per minute during sustained voluntary hyperventilation. These same activities did not elicit any appreciable changes in pacing rate in the remaining two patients whose sensing electrodes were confined to the left hemithorax. Recordings taken from all jive patients while they were standing upright and regularly swinging one upper limb showed an increase in pacing rate of 15 + 6 beats per minute with movement of the right arm and 46 + 8 with movement of the left. These observations establish that the Biorate RDP3 pacemaker is capable of responding both to changes in respiratory rate and to movement of the upper limbs. The sensitivity to limb movement is greatest when the chest wall impedance sensor does not extend across the midline and is most evident when the arm ipsilateral to the pacemaker is swung. This anomalous response may have a profound effect on pacing rate during certain forms of exercise and must be taken into account when programming the pacemaker to meet the heart rate requirements of individual patients.