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Biomedical subjects

D H Bennett

Publications and source records attributed to D H Bennett.

At least 55 records · Page 3Linked to original sources
PubMed1991

Paucity of risk factors in women with angina and normal coronary angiograms.

A significant proportion of women who undergo coronary arteriography for investigation of angina have normal coronary angiograms. We wanted to test the hypothesis that screening women with risk factors for coronary arterial disease would reduce the need for subjecting them to this invasive procedure. Comparisons were made between 100 women with normal coronary angiograms and 100 women with angiographic evidence of coronary arterial disease. Both groups had presented with angina and had undergone coronary angiography in 1985 or 1986. Women with angina and normal coronary angiograms had fewer risk factors than those with coronary arterial disease. They were younger (mean 49.0 and 55.9 years, respectively), had less severe angina on presentation (atypical or mild angina: 35% vs 16%), were less likely to have a family history of myocardial infarction (12% vs 53%), were more likely to have never smoked cigarettes (64% vs 13%), and fewer of them had a serum cholesterol in excess of 6 mmol/l (36% vs 64%). Five independent predictors of coronary arterial disease were identified; family history, myocardial infarction, age, hypertension and smoking habit. No women with angina and abnormal coronary angiograms were found to be free of risk factors, whereas 42% of women with angina and normal coronary angiogram were free of risk factors. The data suggests that coronary angiography will probably be normal in women with angina who are free of risk factors.

Adult↗
PubMed1991

Desirability of immediate surgical standby for coronary angioplasty.

OBJECTIVE: To assess the value of emergency surgical standby for percutaneous transluminal coronary angioplasty. DESIGN: Retrospective review of the major complications of coronary angioplasty in a regional cardiac centre. SETTING: All angioplasties were performed in the cardiac catheterisation laboratory of Wythenshawe Hospital with surgical standby in an adjoining operating theatre. PATIENTS: 1262 vessels were dilated in 1032 patients (mean age 53 years) between 1984 and 1989. MAIN OUTCOME MEASURES: In-hospital mortality from emergency surgical revascularisation after angioplasty; the rate of myocardial infarction and overall morbidity. RESULTS: Coronary angioplasty achieved primary success in 90% of cases. Thirty eight (3.7%) patients (five women (mean age 55.8) and 33 men (mean age 53.0] were referred for urgent surgical revascularisation--36 direct to operation and two within 24 hours. All patients survived surgery. Five of the 38 had had a previous angioplasty to the same vessel and one had had previous coronary artery grafts. Four of the 38 had an angioplasty for unstable angina. Eighteen had single, 13 double, and seven triple vessel coronary artery disease. The target vessel was the left anterior descending in 25, right coronary artery in nine, circumflex in three, and the left anterior descending and circumflex coronary arteries in one. Five required external cardiac massage on the way to the operating theatre; two of them had a left main stem occlusion. Four internal mammary artery and 60 reversed saphenous vein grafts were implanted (1.6 per patient). Complete revascularisation was achieved in 36 (94.7%) patients. Q wave myocardial infarction occurred in six (15.8%). The final outcome was: none dead, three patients with angina, one late death, one cerebrovascular accident, one late operation for a new left anterior descending lesion, two patients on diuretics with or without an angiotensin converting enzyme inhibitor. One orthotopic transplant was performed in a patient in whom cardiogenic shock developed after the left anterior descending coronary artery became occluded 72 hours after angioplasty. CONCLUSION: There was no surgical mortality and low morbidity among patients for whom immediate surgical cover was requested.

Angioplasty, Balloon, Coronary↗
PubMed1990

Monitoring the effect of heparin by measurement of activated clotting time during and after percutaneous transluminal coronary angioplasty.

The anticoagulant effect of heparin during percutaneous transluminal coronary angioplasty was monitored by measurements of the activated clotting time in two studies that compared the effects of a single bolus of heparin with those of a bolus of heparin combined with a continuous infusion of the drug. In a preliminary study 40 patients received a single heparin bolus of 10,000 units (protocol I) and a further 40 patients received both a heparin bolus of 10,000 and a continuous infusion of heparin at a rate of 2000 units per hour (protocol II). During the first 45 minutes, nine patients (23%) in protocol I but only two patients (5%) in protocol II were found to be inadequately anticoagulated. For 24 hours after angioplasty both groups received an infusion of heparin at the rate of 2000 units per hour which led to consistent anticoagulation in 73 (91%) of patients. In a subsequent randomised study, 40 patients received heparin according to either protocol I or II. Protocol II was again found to lead to a higher rate of adequate anticoagulation. During the first 60 minutes 11 patients (55%) in protocol I but only three patients (15%) in protocol II were inadequately anticoagulated. In addition, the activated clotting time of arterial blood in the first 30 minutes was significantly higher than that of venous blood in 70% of the patients. A bolus of heparin (10,000 units) together with an infusion of 2000 units per hour should be routinely given during coronary angioplasty. The effects of heparin, which can vary considerably from patient to patient, should be monitored by the measurement of the activated clotting time of arterial blood.

Adult↗
PubMed1989

The impact of a manufacturer's revision of pacemaker service life on the workload of a large pacing center.

In certain batches of a manufacturer's pacemakers, inadequate insulation of the battery cell feed-through mechanism led to internal short-circuiting and premature battery depletion. We describe the impact of the consequent reduction in service life and recommended close supervision of these generators on the follow-up clinics and inpatient workload at a large pacing center. One-hundred and ninety patients had Cordis Gamma series pacemakers implanted between September 1981 and July 1985; 135 have had to undergo premature generator replacement. Eleven of these pacemakers had developed early depletion of rate and 12 no-output failure. Within 3 months of their generator change, 12 patients developed wound sepsis, three of them requiring further system replacement. We calculate that at least 540 extra outpatient appointments, 400 in-hospital patient days and 12 full working days in one of our catheterization laboratories were required to deal with the problems. The pacemaker industry, as well as doctors and technicians involved in pacemaker purchase and implantation, should be aware of the consequences of a major recall not only on workload but also on patient morbidity and anxiety.

Electric Power Supplies↗
PubMed1989

Oesophageal function in patients with angina pectoris: a comparison of patients with normal coronary angiograms and patients with coronary artery disease.

Oesophageal function was assessed in 52 patients with angina pectoris whose coronary angiograms were completely normal and in 21 patients with angina pectoris who had significant coronary artery disease. During a standard oesophageal manometric study, abnormalities were found in 23 (44%) patients with normal coronary angiograms but in only 2 (10%) patients with coronary artery disease (p less than 0.01). Twenty-four (46%) patients with normal coronary angiograms were found to have gastro-oesophageal reflux disease during 24-hour oesophageal pH monitoring. Of the 52 patients with normal coronary angiograms, 19 (37%) had gastro-oesophageal reflux disease and abnormal oesophageal motility, 5 (10%) had gastro-oesophageal reflux disease alone, and 7 (13%) had oesophageal motility disorder alone. The use of provocation procedures, including intravenous edrophonium during oesophageal manometry and treadmill exercise testing during pH monitoring, enabled the oesophageal abnormality to be demonstrated simultaneously with chest pain in 25 of these 31 patients. Typical angina pectoris, coincident with abnormal oesophageal motility, was precipitated in a subgroup of patients who had been shown to have oesophageal manometric abnormalities and gastro-oesophageal reflux disease by the infusion of hydrochloric acid into the oesophagus; both the chest pain and manometric abnormality resolved following the oral administration of antacid.

Adult↗
PubMed1988

Actuarial analysis of late results after closed mitral valvotomy.

The long-term results of closed mitral valvotomy performed between 1978 and 1985 in 198 patients with noncalcific mitral stenosis were analyzed. Follow-up data were available on 185 patients (93%); 1 patient died in the postoperative period, and 12 foreign patients were lost to follow-up. At the 4-year and 8-year intervals, 91% and 80% of patients, respectively, were event free (not in need of further operative procedures). By multivariate analysis, the factor preoperative mild mitral regurgitation showed a tendency to influence the event-free period. By univariate analysis, postoperative mitral regurgitation significantly reduced the event-free period. Twenty-one patients subsequently underwent mitral valve replacement; 8 for mitral regurgitation, 10 for mitral stenosis, and 3 for mixed mitral regurgitation and stenosis. By multivariate analysis, the reason for reoperation significantly influenced the length of the event-free period. The patients with mitral regurgitation required mitral valve replacement sooner than those with mitral stenosis. Advanced age, sex, previous valvotomy, preoperative New York Heart Association Functional Class, low mitral valve leaflet excursion, and pulmonary hypertension had no influence on the long-term result.

Actuarial Analysis↗
PubMed1988

Angina-like chest pain: a joint medical and psychiatric investigation.

Sixty three patients with chest pain typical of angina and who had normal coronary angiograms were investigated for left ventricular, oesophageal and psychiatric abnormalities. An additional 21 patients, age and sex matched, who had angina and significant coronary artery disease were also studied. Eighty six per cent of the 63 patients without evidence of coronary artery disease could be demonstrated to have a physical abnormality (left ventricular dysfunction in 35%, oesophageal disorder 51%). There was, however, a wide variation in the incidence of psychiatric morbidity between the diagnostic subgroups-18% in left ventricular dysfunction, 29% in those with coronary artery disease and 59% in patients with oesophageal disorders (P less than 0.01). Thus failure to identify left ventricular dysfunction and inclusion of such subjects in psychological assessments of 'angiogram-negative' chest pain might give misleading results. This study confirms that patients with angina and normal coronary angiography have a high incidence of oesophageal disorders. However psychiatric illness is also common in this group of subjects and management needs to take both these factors into account.

Angina Pectoris↗
PubMed1987

Exertional gastro-oesophageal reflux: a mechanism for symptoms in patients with angina pectoris and normal coronary angiograms.

During 24 hour oesophageal pH monitoring 52 patients who had angina pectoris and normal coronary angiograms underwent exercise testing, as far as their symptoms allowed, on a treadmill to determine whether gastro-oesophageal reflux occurred during exertion. In 11 patients the 24 hour oesophageal pH score was abnormally high; 10 of these showed exertional gastro-oesophageal reflux, and in nine this was associated with their usual chest pain. A further 13 patients had a normal 24 hour pH score but had exertional reflux coincident with chest pain during exercise testing. The mean lower oesophageal sphincter pressure in both of these groups of patients was appreciably lower than that in 28 patients who had a normal 24 hour pH score and no exertional reflux. These findings suggest that exertional gastro-oesophageal reflux accounts for the symptoms of a large proportion of patients who have angina pectoris and normal coronary angiograms and that oesophageal pH monitoring during exercise testing on a treadmill enables this group of patients to be identified.

Adult↗
PubMed1987

The effects and dose-response relationship of xamoterol in patients with ischaemic heart disease.

1. In a double-blind placebo controlled four-way crossover study the effects and dose response relationships of xamoterol were studied in nine patients with angina and dyspnoea secondary to chronic left ventricular dysfunction. The duration of exercise on a treadmill and heart rate were measured at the end of each phase of the study at 2 h and 24 h after dosing. 2. Xamoterol at 200 mg and 400 mg orally once daily had no effect on the mean resting heart rate but there was a small (5.7 beats min-1) but significant reduction in resting heart rate on 600 mg at 2-2.5 h after dosing. All three doses of xamoterol significantly reduced the maximum exercise heart rate at 2-2.5 h after dosing. 3. Xamoterol at all three doses significantly increased exercise duration at 2-2.5 h after dosing but not at 24 h. 4. Mean plasma xamoterol concentration at both 2-2.5 h and 24 h after dosing were dose related. The EC50 for xamoterol is 33.5 ng ml-1, where EC50 is the effective plasma concentration required to produce 50% of the maximum effect on exercise heart rate.

Adrenergic beta-Agonists↗
PubMed1987

Left ventricular function and oesophageal function in patients with angina pectoris and normal coronary angiograms.

Left ventricular function and oesophageal function (including oesophageal manometry and pH monitoring) were investigated and a psychiatric assessment carried out in 63 patients with angina pectoris and normal coronary angiograms. Twenty two (35%) patients had regional abnormalities of left ventricular wall motion (group A). Thirty six (57%) patients had an oesophageal abnormality (group B); 19 patients had gastro-oesophageal reflux and abnormal oesophageal motility, five had gastro-oesophageal reflux alone, and 12 had abnormal oesophageal motility alone. Only four had regional abnormalities of the left ventricular wall and abnormal oesophageal function. In nine (14%) patients left ventricular and oesophageal function were normal (group C). Psychiatric morbidity was significantly less common in group A than in groups B and C and was similar in group B and group C. A definite abnormality of left ventricular function, oesophageal function, or psychiatric morbidity is present in a high proportion of patients with angina pectoris and normal coronary angiograms and in some instances this may lead to specific treatment. If quantitative assessment of left ventricular function is normal, oesophageal investigations should be performed. Endoscopy of the upper gastrointestinal tract may demonstrate oesophageal disease, but, if findings are normal, oesophageal manometry and ambulatory oesophageal pH monitoring (including during treadmill exercise testing) should be carried out.

Adult↗
PubMed1986

Left ventricular dysfunction in patients with angina pectoris and normal coronary angiograms.

Left ventricular function was assessed in 201 patients who presented with angina pectoris and who were subsequently found to have completely normal coronary angiograms. Left ventricular angiograms from 187 patients were suitable for analysis of systolic regional wall motion; 121 were found to be normal and 66 had a total of 115 hypokinetic segments. Patients with hypokinesia had a significantly higher left ventricular end systolic volume and a significantly lower left ventricular ejection fraction and exercise capacity than those in whom regional wall motion was normal. Thirty one per cent of patients with normal wall motion and 30% of those with hypokinesia had a resting left ventricular end diastolic pressure greater than 15 mm Hg. There were significantly more smokers in the group with hypokinetic segments. Thus of patients with angina and normal coronary angiograms, 25% had evidence of left ventricular systolic dysfunction, 20% had evidence of diastolic dysfunction, and 11% had evidence of both systolic and diastolic dysfunction. The results suggest that smoking may be associated with left ventricular regional wall motion abnormalities.

Adult↗
PubMed1986

Exercise capacity and spontaneous heart rhythm after transvenous fulguration of atrioventricular conduction.

Twenty nine patients who had had refractory supraventricular tachycardia were studied 4-36 (mean 16) months after transvenous fulguration of the atrioventricular junction. Twenty two had complete atrioventricular block, five partial atrioventricular block, and two had atrioventricular conduction via an accessory atrioventricular pathway. Though all patients were free of palpitation after the procedure, exertional dyspnoea had developed in 13 and in two patients pre-existing dyspnoea had worsened. During ventricular demand pacing, exercise time was reduced to 43% of the predicted value for their age and sex. The 16 patients with rate responsive pacemakers demonstrated a significantly better but still impaired exercise capacity during "physiological" pacing as compared with their performance during constant rate pacing. In patients with complete atrioventricular block there was an increase in spontaneous ventricular rate during exercise in seven patients and in response to the Valsalva manoeuvre in eight patients. This suggests that the intrinsic ventricular pacemaker is influenced by autonomic nervous system activity in some patients. It is concluded that though transvenous fulguration is successful in controlling tachycardia it may reduce exercise capacity. Most patients remain in complete atrioventricular block after the procedure and, in contrast with the practice as described in early reports, would benefit from "physiological" pacing--though even with this mode exercise capacity is likely to be abnormal.

Adult↗
PubMed1985

Smoking and coronary artery disease assessed by routine coronary arteriography.

The association between extent and duration of smoking habit and severity of coronary atheroma was examined in 387 patients undergoing routine coronary ateriography before valve replacement surgery. Total number of cigarettes smoked in life correlated significantly with severity of coronary artery disease (p less than 0.001) and number of coronary arteries with stenoses of 50% or more (p less than 0.001). Severity of coronary artery disease in current smokers was similar to that in former smokers. Multiple regression analysis showed diastolic blood pressure, cigarette consumption, age, ratio of total cholesterol to high density lipoprotein cholesterol, and history of angina to be the important predictors of severity of coronary artery disease. An estimate of the number of cigarettes smoked in life can be useful in identifying patients with coronary artery disease if used in conjunction with data on other important risk factors.

Arteriosclerosis↗
PubMed1985

Comparison of vitreous carbon and elgiloy transvenous ventricular pacing leads.

In a randomized prospective study of 150 patients, we compared two porous-tipped, finned leads, one with a vitreous carbon tip (surface area = 12 mm2) and the other with an Elgiloy tip (surface area = 8 mm2). We assessed the acute and chronic stimulation thresholds and the ease of implantation of the two leads. The acute current thresholds for the vitreous carbon and Elgiloy-tipped leads were 1.7 +/- 0.5 (+/- SD) mA vs. 1.1 +/- 0.4 mA (0.25 ms pulse width), 1.3 +/- 0.5 mA vs. 0.9 +/- 0.3 mA (0.5 ms), and 1.0 +/- 0.3 mA vs. 0.8 +/- 0.3 mA (0.75 ms), respectively (P less than 0.0005). Impedance at implantation was 473 +/- 121 ohms and 716 +/- 285 ohms (P less than 0.0005) for the carbon-tipped and Elgiloy-tipped leads, respectively. The R-wave amplitudes were 10.2 +/- 5.1 volts and 6.8 +/- 3.0 volts, respectively (P less than 0.0005). Both leads were easy to implant and showed low stable chronic thresholds from 3 weeks after implantation, at which time the stimulation threshold was 1.9 +/- 1.0 volts vs. 1.5 +/- 0.6 volts with the implanted voltage-variable generators and 1.8 +/- 0.8 mA vs. 1.6 +/- 0.6 mA with the implanted current-variable generators. Reoperation for displacement was required for two of the 87 (2.3%) carbon-tipped and 2 of the 67 (3.2%) Elgiloy-tipped leads. There was no exit block nor any other lead-related complication. We conclude that both leads have similar and satisfactory performance.

Aged↗
PubMed1985

Reliability of the evoked response in determining the paced ventricular rate and performance of the QT or rate responsive (TX) pacemaker.

The TX pacemaker uses a conventional transvenous electrode to sense T-waves of paced ventricular complexes and it adapts the pacing rate to varying physiological demands by responding to changes in the QT or, more correctly, the stimulus artifact-to-T-wave (stimulus-T) interval. This pacing system was assessed in 13 patients. The relation between heart rate and stimulus-T interval and the effect of programming on the performance of this pacemaker were studied on several occasions in each patient. Treadmill exercise performance during TX pacing mode was compared with atrial synchronized ventricular (VAT) and asynchronous ventricular demand (VOO and VVI--70 beats per minute) pacing modes. T-wave sensing problems arose in three patients. In one, this was overcome by reducing the pulse amplitude from 5.0 to 2.5 V. In another patient, spontaneous recovery of T-wave sensing occurred 5 months after pacemaker implantation. T-wave sensing deteriorated with the passage of time in most patients. Satisfactory rate response as assessed by treadmill exercise testing and Holter monitoring was achieved in 12 patients through adjustments of two programmable parameters: the slope that defines the alteration in heart rate in response to a millisecond change in stimulus-T interval and the "sensing window" that is the interval during which T-waves can be sensed and a rate response is possible. Exercise performance was significantly better during rate responsive pacing (TX) mode as compared with VVI pacing but was comparable to that during VAT pacing. The resting heart rate/stimulus-T interval can be described by the following linear regression equation: stimulus-T interval = 466 - 1.68 X paced-rate, r2 = -0.62. This relation, however, was subject to wide inter- and intra-patient variation. Consequently, given identical programmed parameters and exercise protocol, the chronotropic response differed significantly from patient to patient and in the same patient from one occasion to another. Our results show that a physiologically beneficial chronotropic response can be achieved in most patients. However, reprogramming, based on results of exercise tests and Holter monitoring, may be necessary to adjust for changes in T-wave sensing and the heart rate/stimulus-T interval relation and, thus to ensure that the pacemaker continues to function optimally.

Adolescent↗