Biomedical subjects

S Croal

Publications and source records attributed to S Croal.

3 recordsLinked to original sources

PubMed1995

Esophageal countershock: anthropometric determinants of impedance.

OBJECTIVE: To examine the use of a novel esophageal electrode system for countershock of atrial and ventricular tachyarrhythmias, with particular regard to the measurement of transesophageal and transthoracic impedances and their association with anthropometric variables. METHODS: Transesophageal cardioversion was attempted during 131 episodes of arrhythmia in 105 patients (including 109 episodes of atrial fibrillation). The esophageal system also used in 29 patients undergoing electrophysiologic studies for investigation of ventricular tachyarrhythmias. Transesophageal and transthoracic impedances were estimated during passage of a high-frequency, low-amplitude current between the respective electrodes. Impedance estimates were associated with anthropometric measurements using linear regression (least-squares method). RESULTS: In the group of patients undergoing attempted transesophageal cardioversion, the mean estimated transesophageal impedance of 52.6 +/- 11.7 omega was significantly lower than the mean estimated transthoracic impedance of 63.1 +/- 16.4 omega (n = 104, p < 0.01). For all the patients, transesophageal impedance was associated with weight, body mass index, and chest circumference (all r > or = 0.65, p < 0.01). Transthoracic impedance was associated with the same factors (all r > or = 0.55, p < 0.01). CONCLUSION: This esophageal electrode system results in lower impedance values for countershock between the esophagus and the cutaneous cardiac apex in comparison with standard transthoracic cutaneous electrode placement. Both techniques are dependent on anthropometric factors.

Adult↗

PubMed1993

Transesophageal cardioversion.

With the use of a novel quadripolar esophageal electrode system, we have attempted 131 transesophageal cardioversions in 105 patients: 109 episodes were atrial fibrillation, 16 episodes were atrial flutter, 2 episodes were supraventricular tachycardia, and 4 episodes were ventricular tachycardia. The mean predicted transesophageal impedance (+/- SEM) of 52.6 +/- 1.1 omega was significantly lower than the mean predicted transthoracic impedance (+/- SEM) of 63.1 +/- 1.6 omega (n = 104; p < 0.01). Of the 88 patients who presented with atrial fibrillation as the initial arrhythmia, successful transesophageal cardioversion (maximal delivered transesophageal energy of 100 J in 84 patients and 200 J in 4 patients) was recorded in 70 (79.5%); transesophageal cardioversion required a mean delivered energy of 63.1 +/- 4.2 J and a mean peak current of 20.3 +/- 0.6 A. Transthoracic countershock (maximal delivered energy of 360 J) was attempted in 17 of 18 patients when the transesophageal approach had been unsuccessful; countershock was successful in 10 patients, which yielded an overall success rate of 92.0% (mean successful delivered energy [transesophageal and transthoracic] of 85.3 +/- 7.8 J). All episodes of atrial flutter, supraventricular tachycardia, and ventricular tachycardia were successfully terminated with the use of the esophagus. This esophageal electrode system permits low-energy countershock of atrial and ventricular tachyarrhythmias.

Adult↗

PubMed1993

Strain gauge plethysmography for the detection of deep venous thrombosis.

Deep venous thrombosis is a widely recognized medical problem which results in significant morbidity and mortality. Venography is the current 'gold standard' diagnostic test for deep venous thrombosis; however it is costly, invasive and is unnecessarily performed in 50% of cases. This paper describes a self-contained, non-invasive system for automatic venous occlusion plethysmographic measurement and analysis. An examination of 274 symptomatic limbs was conducted using strain gauge plethysmography and a subsequent venographic examination was then performed. The plethysmographic results were then compared with venography so as to develop a means of discrimination for thrombotic and non-thrombotic limbs. Strain gauge plethysmography using the Belfast DVT Screener yielded a sensitivity of 100% and a sensitivity of 66.3% for proximal segment DVT. The efficacy of the discriminatory algorithm was then tested for the diagnosis of DVT in a further 101 symptomatic patients. A sensitivity of 94.7% and a specificity of 81.7% were observed for strain gauge plethysmography for proximal segment thrombosis in this patient group. The Belfast DVT Screener is highly sensitive for deep venous thrombosis and may be used to reduce the need for venography, which is of benefit to both the patient and clinician.

Adult↗