Biomedical subjects

R Cowell

Publications and source records attributed to R Cowell.

At least 19 recordsLinked to original sources

PubMed1994

Postoperative hemodynamic improvement with paced linkage of the donor and recipient hearts following heterotopic cardiac transplantation.

It has been shown that following heterotopic heart transplantation the recipient left ventricle ejects more effectively when it contracts out of phase with the donor left ventricle. However, this is rarely the situation, as the two hearts beat independently of one another and the denervated donor heart tends to beat faster than the recipient. In this study the hemodynamic effects of connecting the two hearts by an external temporary dual-chamber pacemaker were evaluated. The donor right ventricle was sensed and the recipient right atrium paced after a timed delay. The delay was adjusted so that recipient systole coincided with donor diastole. Eleven patients were studied in the first postoperative day. Pacing resulted in an improvement in cardiac output from 5.0 to 5.6 l/min (p = 0.003) and a reduction in pulmonary capillary wedge pressure from 16 to 12 mmHg (p = 0.0035). This was associated with a 35% reduction in inotrope requirements. It is concluded that sequential pacing of the two hearts is a useful adjunct to inotropic support in the postoperative period.

Cardiac Output↗

PubMed1994

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.

Atrioventricular Node↗

PubMed1994

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.

Adult↗

PubMed1993

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

Sensor cross-checking within dual sensor rate 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.

Angina Pectoris↗

PubMed1992

After ISIS-3.

Explore the source record for details and available documents.

Cerebrovascular Disorders↗

PubMed1992

Right atrial thrombus migration during echocardiography: a case for urgent intervention.

A 65-year-old woman presented with increasing shortness of breath, chest pain and ST-T wave abnormalities on the electrocardiogram suggestive of unstable angina. Cross-sectional echocardiography performed to assess wall-motion abnormality and left ventricular function revealed a pedunculated right atrial thrombus prolapsing into the right ventricle which suddenly dislodged and migrated into the pulmonary circulation during the examination. A diagnosis of recurrent pulmonary thromboembolism was made, necessitating urgent pulmonary angiography with infusion of streptokinase. The patient made an uneventful recovery.

Aged↗

PubMed1987

Severe hypokalaemia from kaolin and morphine abuse.

A 34 year old man, registered disabled as a result of muscle weakness, was admitted to hospital because of increasing weakness. He had profound hypokalaemia and admitted to taking up to 1400 ml of kaolin and morphine mixture daily. After considerable potassium replacement muscle power recovered completely. The hypokalaemia is likely to have been caused by the combination of liquorice extract and sodium bicarbonate in kaolin and morphine.

Adult↗

PubMed1983