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Biomedical subjects

S W Webb

Publications and source records attributed to S W Webb.

35 records · Page 2Linked to original sources
PubMed1981

Discrete subaortic stenosis.

Data concerning 17 consecutive patients with discrete subaortic stenosis are recorded. Twelve patients underwent operative resection of the obstructing lesion. Of these all except one were symptomatic and all had electrocardiographic evidence of left ventricular hypertrophy or left ventricular hypertrophy with strain. They had a peak resting systolic left ventricular outflow tract gradient of greater than 50 mmHg as predicted from the combined cuff measurement of systolic blood pressure and the echocardiographically estimated left ventricular systolic pressure and/or as determined by cardiac catheterisation. The outflow tract gradient as predicted from M-mode echocardiography and peak systolic pressure showed close correlation with that measured at cardiac catheterisation or operation. During the postoperative follow-up from one month to 11 years, of 11 patients, one patient required a further operation for recurrence of the obstruction four years after the initial operation. All patients are now asymptomatic. Five patients have not had an operation. The left ventricular outflow tract gradient as assessed at the time of cardiac catheterisation was greater than 50 mmHg. One patient has been lost to follow-up. The remaining four have been followed from four to eight years and have remained asymptomatic and the electrocardiograms have remained unchanged. Careful follow-up of all patients is essential with continuing clinical assessment, electrocardiograms, M-mode and two-dimensional echocardiograms, and if necessary cardiac catheterisation. Prophylaxis against bacterial endocarditis is also essential.

Adolescent↗
PubMed1978

Clinical experience with transvenous atrial pacing.

Twelve patients were paced with a transvenous J-shaped bipolar electrode positioned in the right atrial appendage. All had chronic sinoatrial dysfunction and 5 had paroxysmal atrial arrhythmia: 2 had recent myocardial infarction, 1 angina decubitus, and 1 ventricular pre-excitation. Atrioventricular sequential pacing was employed in this last patient and this mode of pacing was substituted for atrial pacing in one other. The remaining 10 patients were paced from the atrium only. Electrode displacement occurred in 2 patients and 2 others had a rise in pacing threshold. After repositioning the electrode or substituting a more powerful pacemaker, sustained atrial capture was achieved in 3 of these 4. Sensing of spontaneous P waves was present constantly in 4 and variably in 3 of 9 patients. Symptomatic improvement was obtained in 10 patients. A bipolar pacemaker with a variable output voltage and a relatively high demand sensitivity is optimal for atrial pacing. Measurements of intra-atrial voltage with various electrode configurations in 7 patients suggest that atrial sensing may more often be achieved when the reference electrode is situated in the upper part of the right atrium than when it is close to the electrode tip in the atrial appendage.

Aged↗
PubMed1977

Transthoracic ventricular defibrillation in adults.

A prospective study of the energy required for transthoracic ventricular defibrillation in adults showed that in 42 (81%) out of 52 episodes of ventricular fibrillation shocks of 100 watt-seconds (Ws) of stored energy were successful. Out of 233 episodes, 222 (95%) were converted by 200 W s shocks. Among patients in whom primary ventricular fibrillation occurred within one hour of the onset of acute myocardial infarction, 200 W s shocks were successful in 40 (98%) out of 41 episodes. When low-energy shocks failed, a stored energy of 400 W s invariably succeeded. The need for large and expensive defibrillators that store more than 400 W s and are less readily available is therefore questioned.

Adult↗
PubMed1975

Electrical requirements for ventricular defibrillation.

Most deaths from ischaemic heart disease are sudden, occur outside hospital, and result from ventricular fibrillation. But defibrillators have only limited availability because of their size and weight. A miniature defibrillator has been developed. A singe low-energy shock succeeded in removing ventricular fibrillation in 73 out of 82 episodes, and a further shock was successful in seven more episodes. Primary ventricular fibrillation probably always responds to low-energy electrical shocks, which challenges the conventional view that correction of ventricular fibrillation requires high-energy direct-current shock. Thus even smaller and lighter defibrillators are possible. Furthermore low-energy shocks cause less myocardial damage.

Body Weight↗
PubMed1972

Autonomic disturbance at onset of acute myocardial infarction.

Of 74 patients seen within 30 minutes of the onset of acute myocardial infarction 68 (92%) had signs of autonomic imbalance. Excessive vagal activity was evident in 41 (55%) and there was sympathetic overactivity in 27 (36%). The high incidence of sudden death in the acute phase of a coronary attack probably results from the electrical imbalance caused by autonomic disturbance. This disturbance must therefore be taken into account in any prophylactic regimen against the lethal early ventricular dysrhythmias.

Acetanilides↗
PubMedDate not supplied

Control of heart rate during movement in acute myocardial infarction.

Among patients with acute myocardial infarction and a normal heart rate and blood pressure, a high incidence of sympathetic overactivity was recorded during transport. The combined administration of atropine and sotalol had no significant effect on the mean maximum heart rate on movement. However, this drug combination prevented excessive slowing of the heart rate. Sotalol caused a significant reduction in the mean maximum heart rate on movement. The side-effects were minimal. 10% of patients who received sotalol required atropine for the correction of bradyarrhythmia.

Adult↗
PubMedDate not supplied

Transthoracic ventricular defibrillation in the adult.

Since the lower the energy used, the less the possible myocardial damage, two studies of 214 patients in ventricular fibrillation (VF) were conducted, using two types of defibrillators each charged to 200 Wsec and 100Wsec. In the first study, each defibrillator was charged to 200 Wsec (150-165 Wsec delivered). Up to three 200-Wsec shocks successfully converted 222 of 233 VF episodes. In 199 episodes, a single shock successfully removed the fibrillation. In 48 episodes in patients weighing more than 80 kg, VF was removed in 43 (90 percent). In the second study, from a stored energy of 100 Wsec, 74 to 82 Wsec of energy were delivered in the initial shock to treat 161 VF episodes in 94 patients. The first shock was successful in 101 (63 percent) of the 161 episodes. Up to three 100-Wsec shocks achieved 81 percent conversion in 52 episodes. A third 100-Wsec shock seldom succeeded. Using a sequence of 100 - 200 - 400 Wsec shocks, 93 (91 percent) of 102 episodes were successfully converted. There was not a single instance of failure to remove VF among the 214 patients with a maximal delivered energy of 330 Wsec. Thus, the direction towards the production of larger instruments storing more than 400 Wsec energy seems unwarranted.

Adult↗