Biomedical subjects

P M Nichol

Publications and source records attributed to P M Nichol.

12 recordsLinked to original sources

PubMed1994

Verapamil improves left ventricular filling and exercise performance in hypertensive and normotensive elderly individuals.

OBJECTIVE: To study the effect of verapamil slow release (SR) upon left ventricular diastolic function and exercise capacity in newly diagnosed older hypertensive subjects compared with normotensive elderly and young controls. DESIGN: Cross-sectional prospective trial. INTERVENTIONS: Doppler echocardiography at rest and graded maximal exercise testing (with breath-by-breath gas analysis) before and 4 h after administration of oral verapamil SR 240 mg, and before and after 12 weeks of daily medication. MAIN RESULTS: Verapamil administration normalized resting blood pressure in the older hypertensive group, but did not alter blood pressure in older normotensive or young groups. Resting heart rate was not altered in any of the groups. Both the older hypertensive and normotensive groups showed improvement in measures of diastolic filling after verapamil ingestion. Specifically, the older hypertensive group showed significantly faster isovolumic relaxation time (IVRT). In the older normotensive group IVRT was not changed, but the E:A ratio (the ratio of early to late peak transmitral flow velocity) was increased after verapamil. No differences were observed between the effects of verapamil after acute ingestion (4 h) or with chronic use (12 weeks) in any of the variables measured. In the younger group diastolic filling was not altered after verapamil ingestion. In both the elderly normotensive and hypertensive groups maximum oxygen consumption was significantly improved following verapamil ingestion. Again, no differences were observed between 4 h and 12 weeks. In the younger subjects exercise performance was not changed after verapamil ingestion. CONCLUSIONS: Verapamil SR improved left ventricular diastolic function and exercise performance in hypertensive and normotensive elderly individuals. Verapamil normalized blood pressure in the hypertensive subjects, but did not alter blood pressure in the normotensive elderly or younger subjects.

Adult↗

PubMed1988

Comparison of cardiovascular response to passive tilt in young and elderly men.

To test the hypothesis that altered hemodynamic responses to postural changes are associated with aging, cardiovascular responses to head-up tilt (HUT) and head-down tilt (HDT) were examined in 12 healthy young (average age, 24.6 +/- 1.7 years) and 12 healthy elderly (average age, 68.6 +/- 2.2 years) men. Subjects were passively tilted from supine to 30 degrees, 60 degrees, and 90 degrees HUT and HDT. Responses to these perturbations were determined 5 min after tilting with measures of heart rate (HR), blood pressure (SBP, DBP), and echocardiographically determined left ventricular diameter in systole and diastole (LVIDs, LVIDd). In HUT there were no significant age effects. In both young and elderly, SBP decreased significantly (p less than 0.05), and DBP and HR increased significantly. Ejection fraction (EF), mean arterial blood pressure (MABP), and rate-pressure product (RPP) were unchanged in both groups. In HDT, the hemodynamic responses of the young and elderly were in opposite directions and significant age effects were found for SBP, DBP, HR, LVIDs, EF, MABP, and RPP. In HDT, the young appear to increase cardiac output primarily due to an increase in EF and end-diastolic volume (LVIDd), while HR is unchanged and SBP is decreased. MABP is unchanged, suggesting a small decrease in total peripheral resistance. The elderly may increase cardiac output slightly, owing to an increase in LVIDd with no change in EF, and a large increase in HR. Afterload increased markedly, therefore attenuating any increase in cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

Dopamine: its potential for inducing ischemic left ventricular dysfunction.

As an agent potentially capable of inducing ischemia in patients with coronary artery disease, dopamine administered intravenously was evaluated as a pharmacologic stress agent by supine radionuclide angiography, and the results were compared with ergometer exercise. In a preliminary group of 11 subjects (4 normal subjects and 7 patients with coronary disease), dopamine alone was administered in increments of 2.5 micrograms/kg per min to a maximum of 15 micrograms/kg per min. There were significant differences between exercise and dopamine in maximal stress heart rates, 129.3 +/- 30.0 versus 88.0 +/- 35.8 beats/min (p less than 0.05) in normal subjects and 118.9 +/- 21.1 versus 87.6 +/- 22.6 beats/min (p less than 0.05) in patients with coronary disease, as well as in maximal stress rate-pressure products, 213.3 +/- 51.4 versus 155.0 +/- 52.5 mm Hg/min X 10(2) (p less than 0.02) in normal subjects and 216.0 +/- 45.6 versus 161.0 +/- 48.6 mm Hg/min X 10(2) (p less than 0.003) in patients with coronary disease. As a result, in these patients the ejection fraction response was significantly different: -3.3 +/- 4.5% with exercise versus + 6.3 +/- 4.6% with dopamine (p less than 0.05). In a second group of 41 subjects (9 normal subjects and 32 patients with coronary disease), atropine (0.6 mg) was administered intravenously before and after every second dopamine dose increment. This produced statistically similar maximal stress heart rates as compared with exercise in all subjects, rate-pressure products in normal subjects and slightly higher values with dopamine in patients with coronary disease: 200.3 +/- 47.2 versus 183.1 +/- 43.0 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗

PubMed1984

Increased prevalence of mitral valve prolapse in patients with migraine.

Patients with classic migraine (69 women and 31 men) selected randomly from a practice list of over 1000 were matched for age, sex and neighbourhood with 100 people who did not have headache problems, and both groups underwent M-mode and two-dimensional echocardiography and clinical examination by cardiologists blinded to the subjects' clinical status. The mean ages were 34.9 +/- 11.3 years for the migraine group and 33.1 +/- 9.9 years for the control group. Definite and possible mitral valve prolapse (MVP), diagnosed according to predefined echocardiographic criteria, were found about twice as often in the migraine group as in the control group (in 15 v. 7 and 16 v. 8 patients respectively); the echocardiograms were definitely normal in 69 migraine patients and 85 controls (chi 2 = 8.39, p less than 0.025). Altogether 25% of the migraine group and 11% of the control group had evidence of MVP from a combination of the echocardiographic and auscultatory findings (chi 2 = 5.72, p less than 0.025). The odds ratio was 2.7, with 95% confidence limits of 1.17 and 6.29. The association between migraine and MVP has implications for the understanding of platelet abnormalities and episodes of cerebral ischemia occurring in both these conditions.

Adult↗

PubMed1984

Effects on ventricular function of disopyramide, procainamide and quinidine as determined by radionuclide angiography.

To evaluate the effects of the 3 commonly used antiarrhythmic agents--disopyramide, procainamide and quinidine--on left ventricular (LV) function, these 3 agents were administered in random sequence after control radionuclide angiography performed at rest and during exercise in 17 patients. Drug dosages were tailored to achieve therapeutic blood levels 5 minutes before and 2 to 3 hours after drug administration. The mean dose of disopyramide was 141 +/- 26 mg every 6 hours, procainamide, 441 +/- 100 mg every 4 hours, and quinidine, 401 +/- 101 mg of the gluconate preparation every 6 hours. The patients received the appropriate dosage for 7 or more days before repeat radionuclide angiography was performed. The ejection fraction at rest was: control 60 +/- 13%, disopyramide 55 +/- 11%, procainamide 58 +/- 11%, and quinidine 59 +/- 12%. The exercise ejection fraction was: control 61 +/- 14%, disopyramide 58 +/- 13%, procainamide 58 +/- 12% and quinidine 61 +/- 13%. In neither case, at rest nor during exercise was there any significant difference observed between any of the agents or between any individual agent and control. However, at rest 8 subjects had a 5% or more decrease from the control value with disopyramide, 5 had a 5% or more decrease with procainamide and 6 had a 5% or more decrease with quinidine, whereas during exercise the decreases were 8, 6 and 5%, respectively. These values were not statistically different but suggest that caution should be taken in administering all 3 agents, particularly to patients with impaired LV function, because individual sensitivity to a given agent may precipitate a significant decline in LV function.

Adult↗

PubMed1984

The role of Swan-Ganz catheterization in severe pregnancy-induced hypertension.

Swan-Ganz catheterization was performed in 15 postpartum women who presented with severe pregnancy-induced hypertension at a mean gestational age of 31.5 weeks. The mean arterial pressure on presentation was 137.6 torr (range, 116 to 167 torr), and it remained at approximately 115 torr for the next 72 hours. Serial pulmonary capillary wedge pressure, cardiac output, and colloid oncotic pressure were obtained. The mean pulmonary capillary wedge pressure was 9 torr on insertion of the catheter, and it rose to 13 torr by 36 hours. Three patients whose pulmonary capillary wedge pressure was higher than the mean developed pulmonary edema. The mean colloid oncotic pressure was 14.14 torr. We found that hemodynamic monitoring and determinations of colloid oncotic pressure were useful additions to the clinical examination in the postpartum management of patients with severe pregnancy-induced hypertension. Our patients had a broad range of central volume status, cardiac output, and systemic vascular resistance, and the management was tailored accordingly. Although most patients had hyperdynamic pulmonary cardiac function, three developed edema at a lower pulmonary capillary wedge pressure because of decreased colloid oncotic pressure and possibly increased capillary permeability.

Adolescent↗

PubMed1980

Further evidence relating mitral-valve prolapse to cerebral ischemic events.

Echocardiography demonstrates prolapse of the mitral valve in at least 5 per cent of the population. Since some observations have linked this condition to stroke, we studied its incidence in two groups of patients with cerebral ischemia. The older group contained 141 patients over 45 years of age (mean, 64.7 years) who had transient ischemia or partial stroke. Prolapse was found in eight (5.7 per cent) of these patients and in 10 (7.1 per cent) of 141 age-matched controls. The second group contained 60 patients who had transient ischemia or partial stroke and were under 45 years old (mean 33.9 years). Prolapse was detected in 24 patients (40 per cent) but in only five (6.8 per cent) of 60 age-matched controls (mean age, 33.7 years). The odds ratio, 9.33, was highly significant (P less than 0.001). In six of the 24 patients there were other potential causes for cerebral ischemia leaving 18 whom the only recognizable potential cause was a prolapsing mitral valve (odds ratio, 7.00; P less than 0.001). This study suggests that this entity has a role in cerebral ischemia, at least in younger patients. (N Engl J Med 302:139-144, 1980).

Adult↗

PubMed1980

Superior vena cava syndrome: case report. A complication of permanent transvenous endocardial cardiac pacing requiring surgical correction.

Superior vena cava syndrome developed in a patient in whom an endocardial transvenous pacemaker had been inserted five years previously. Venography demonstrated an obstructing lesion at the junction of the superior vena cava and right atrium. Balloon catheter dilatation failed to afford any relief from her progressive symptoms. Exploration of the area revealed a benign fibrotic lesion encircling the pacemaker lead within the right atrium. Excision of the lesion, removal of the lead, and patching the right atrium with pericardium resulted in rapid cure.

Aged↗

PubMed1980

Gas transport capacity and echocardiographically determined cardiac size in children.

One hundred and seventeen boys (10, 12, and 14 yr of age) were studied to determine the relation between maximal gas transport capacity (VO2 max) and cardiac size and the interaction of growth and physical activity on this relation. VO2 max was measured during treadmill exercise and heart size was obtained during supine rest by M-mode echocardiography. Left ventricular end-diastolic diameter (LVIDd), resting stroke volume (SV), and calculated left ventricular mass (LVM) were highly correlated (0.75 < r < 0.84) with VO2 max within all age categories. Subjects with high VO2 max had significantly (P < 0.05) larger LVIDd, end-diastolic volumes, resting SV, calculated LVM, and, with the exception of the 12 yr olds, larger left ventricular end-systolic diameters and volumes than subjects with lower VO2 max. Multiple linear regression analysis revealed that fat-free weight accounted for most of the variance in VO2 max and that cardiac dimensions were only of minimal importance in determining maximal gas transport capacity in this study. The seemingly good relationship between cardiac dimensions and VO2 max was mainly attributable to the shared influence of body size on both these factors.

Adolescent↗

PubMed1979

Effects of endurance training on left ventricular dimensions in healthy men.

Echocardiography was employed to measure the serial effects of jogging on resting left ventricular dimensions and function. Twelve men were exercised (mean age 36.8 yr) and 10 served as controls (mean age 34.8 yr). Increases of 14 and 18% were observed for predicted aerobic capacity in the training group (TG) after 3 and 6 mo of training, respectively; the control group (CG) displayed a small detraining effect. Echocardiographic findings included a significant (P less than 0.05) reduction in resting heart rate and a moderate increase in stroke volume (SV) in the TG compared to the CG. The increased SV appeared to be due to increased end-diastolic dimensions (LVIDd, LVEDV), secondary to greater ventricular filling rather than a more vigorous ventricular contraction. Posterior wall thickness, septal thickness, and calculated left ventricular muscle mass were not significantly increased in the TG compared to CG after either 3 or 6 mo training. It was concluded that left ventricular structure and resting contractile status are not altered by 6 mo of jogging training in healthy, previously sedentary men.

Heart↗

PubMed1977

Two-dimensional echocardiographic assessment of mitral stenosis.

A real-time, phased-array, two-dimensional echocardiography system was used to assess mitral valve motion in 30 catheterized patients with pure mitral stenosis. Suitable images for analysis of mitral valve motion were obtained in 25 patients. The valve leaflets were most thickened and immobile at the leaflet tips while maximum mobility was at the leaflet body. Diastolic movement of anterior mitral leaflet toward the septum pulled the posterior mitral leaflet mid-portion inferiorly. Systolic bulging of the mid-portion of the anterior mitral leaflet into the left atrium was seen in 40% (10 of 25). Movement of the anterior mitral leaflet in diastole is primarily due to movement of the whole mitral apparatus in patients with mitral stenosis. The anterior mitral leaflet E to F slopes did not correlate (r=0.38) with the mitral valve area determined at catheterization. Planimetry of the mitral valve area directly from the videotape images compared favorably to the valve area determined at catheterization (r=0.95). Thus, mitral valve area determined by this technique is an accurate noninvasive method for assessing the severity of mitral stenosis.¿

Cardiac Catheterization↗

PubMed1976

Noninvasive assessment of mitral insufficiency by transcutaneous Doppler ultrasound.

Instantaneous aortic arch blood velocity was recorded transcutaneously from the suprasternal notch, using a 2.2 MHz Doppler ultrasound unit, in 18 normals and 16 patients undergoing cardiac catheterization who had murmurs of mitral regurgitation. In normals aortic blood velocity rose rapidly in early systole to a midsystolic peak then fell to zero velocity. These roughly parabolic patterns had area ratios beneath the first and second halves of the curves measuring 52:48 +/- 3 (SD). With increasingly severe mitral regurgitation the pattern became skewed leftward such that the percent in the first half of systole ranged from 53-79%. From the angiograms of our sixteen patients an estimate of true percent regurgitation was made using the Fick cardiac output and ventricular volume measurements. When compared with the area under the first half of the velocity curve a strong correlation was found (r = 0.84) indicating that this Doppler technique can be used to evaluate mitral insufficiency.

Adult↗