Biomedical subjects

R I Jones

Publications and source records attributed to R I Jones.

8 recordsLinked to original sources

PubMed1986

Twice-daily verapamil for hypertension: a comparison with propranolol.

Recent reports have confirmed that some slow calcium channel inhibitors have useful antihypertensive properties because they produce dilatation of the peripheral arterioles without reflex tachycardia. Verapamil is such a drug, but its clinical role in the management of hypertension is not clear. An open crossover trial was performed to compare the 24-hour profiles of blood pressure reduction after long-term therapy with a standard beta-adrenoceptor blocker, propranolol, and verapamil. Nineteen patients were studied by continuous ambulatory intraarterial recording and the order of drug administration was determined by random allocation. The drugs were administered 2 times a day and titrated according to casual clinic pressures (propranolol, 40 to 240 mg 2 times a day; verapamil, 120 to 240 mg 2 times a day). Mean hourly blood pressure and heart rate values were obtained over a 24-hour cycle and the responses to isometric and dynamic exercise were also examined. The drugs produced a uniform and comparable reduction in blood pressure throughout the day, together with a reduction in heart rate, which was greater with propranolol. Comparable effects were also seen on the pressor responses to exercise. Both drugs were equally well tolerated and caused no patient withdrawals. Thus, oral verapamil given 2 times a day shows a degree of efficacy similar to that of propranolol and provides 24-hour blood pressure control. This slow calcium channel inhibitor was well tolerated and may be used as initial therapy for hypertension.

Adult↗

PubMed1986

Simultaneous measurement of left ventricular function and myocardial perfusion during a single exercise test: dual isotope imaging with gold-195 m and thallium-201.

The state of left ventricular function and myocardial perfusion are important determinants of prognosis in patients with coronary artery disease and information on both can be valuable for planning individual patient management. We have studied the feasibility of simultaneous measurement of left ventricular ejection fraction with ultra short-lived gold-195 m (half life 30.5 seconds) and myocardial perfusion with thallium-201, at rest and after exercise with a single-crystal gamma camera. The results with first-pass radionuclide angiocardiography (RNA) using gold-195 m at rest were reproducible and agreed closely with the results obtained using technetium-99 m equilibrium radionuclide angiocardiography (r = 0.93). Ejection fraction by first-pass gold-195 m RNA during semi-supine ergometric exercise decreased by greater than 5% in 13 out of 18 patients with coronary artery disease and stable angina. Simultaneous myocardial imaging with thallium-201 was abnormal in all patients. The change in regional wall motion abnormality score during exercise correlated with the change in myocardial perfusion (r = 0.71, P less than 0.01) and with the change in global left ventricular ejection fraction (r = 0.77, P less than 0.001). The widely differing energy levels and half-lives of gold-195 m and thallium-201 made it possible to separate clearly the images due to each radionuclide. This study has demonstrated the feasibility of simultaneous or sequential assessment of left ventricular function and myocardial perfusion during a single exercise test, a technique which can offer advantages in clinical evaluation of patients with coronary artery disease.

Adult↗

PubMed1986

Changes in left ventricular function during exercise and their relation to ST segment changes in patients with angina.

The high count sensitivity of the non-imaging nuclear probe affords the possibility of measuring left ventricular ejection fraction continuously during short term interventions. The nuclear probe was used to examine the pattern of change of left ventricular function during dynamic exercise and its temporal relation to ST segment depression in 12 patients with stable exertional angina. After in vivo blood pool labelling with technetium-99m the left ventricular time-activity waveform was detected by the nuclear probe and was continuously recorded on a strip chart. The 15 beat mean ejection fraction and the ST segment level 80 ms after the J point were measured at rest and every 30 seconds during maximal ergometric exercise and during recovery. The mean ejection fraction was 54.3% (range 46-64%) at rest and fell during exercise in all subjects by a mean of 16.8% (range 6-25%). In contrast, in a control group of 16 healthy male volunteers the mean ejection fraction was 55.9% (range 47-64%) at rest and increased in all by a mean of 10.2% (range 3-19%) during exercise. The difference of ejection fraction response to exercise between the patients and controls was due to pronounced increases in relative end diastolic and especially end systolic volumes in the patients. Relative stroke volume differed between patients and controls only at peak exercise. ST segment depression greater than 1 mm developed in 11 of the 12 patients. A decrease of greater than 5% in ejection fraction occurred within 1 minute of starting exercise in nine of the 12, and in 11 patients it preceded the beginning of ST depression. In most of this selected group of patients the ejection fraction had fallen during exercise before the appearance of ischaemic electrocardiographic changes.

Aged↗

PubMed1986

Left ventricular function during isometric hand grip and cold stress in normal subjects.

Both isometric exercise and cold stress have been suggested as alternatives to dynamic exercise for the detection of obstructive coronary artery disease. A non-imaging nuclear probe was used to measure left ventricular ejection fraction and relative left ventricular volumes continuously during both of these stress tests in 24 normal subjects. There was a significant fall in left ventricular ejection fraction within 15 seconds of subjects starting a two minute isometric hand grip test at 50% maximal voluntary contraction, with a mean (SE) maximal fall of 10% (1.8) after 90 seconds. During two minutes immersion of the hand and wrist in iced water left ventricular ejection fraction fell significantly within 30 seconds with a mean maximal fall of 7% (1.7) after one minute. Nine subjects underwent repeat tests under identical conditions approximately two weeks later. The standard error of the change in ejection fraction on two occasions was 5.4% at rest, 7.0% at the peak of isometric exercise, and 4.8% at peak cold stress. These results indicate that the reproducibility of both of these stress tests is acceptable when they are performed under carefully controlled conditions. The resulting changes in ejection fraction are transient, however, and moreover depend upon the choice of stress protocol. The discrepancies between published reports of such studies in coronary artery disease may be mainly due to methodological differences, and neither test is likely to be of sufficient discriminative ability to distinguish between individuals with obstructive coronary artery disease and normal subjects.

Adult↗

PubMed1986

Ambulatory blood pressure and assessment of pacemaker function.

Ten patients in sinus rhythm with ventricular demand (VVI) pacemakers implanted for the sick sinus syndrome underwent 24 hour ambulatory blood pressure and electrocardiographic recording by a modified version of the Oxford system. Five patients had symptoms of dizziness or presyncope at the time of study and five were symptom free. The onset of pacing was associated with a fall in arterial blood pressure in both groups which was larger in the patients with symptoms, and in these patients the blood pressure recovery consequent on baroreflex activation was delayed by up to fifteen beats. In three of the patients with symptoms the original pacemaker was replaced by an atrioventricular pacing (DVI) device. This abolished symptoms and the initial fall and delayed recovery of blood pressure. Thus it appears that the development of symptoms of hypotension after the onset of ventricular pacing is determined by the rate of the baroreflex response. These symptoms and the haemodynamic consequences may be alleviated by dual chamber pacing.

Aged↗

PubMed1985

Effect of enalapril at rest, during tilt, static and dynamic exercise in systemic hypertension.

Using the "Oxford system" for ambulatory monitoring of direct arterial blood pressure (BP), the hypotensive effect of enalapril (20 to 40 mg/day), was assessed in 15 patients with essential hypertension. BP was reduced by enalapril throughout the 24 hours of study. A within-patient comparison of corresponding mean hourly systolic and diastolic BP values showed a reduction from (p less than 0.05 to p less than 0.001) for 18 of the 24 hours. Four patients had an increase in BP during treatment with enalapril. There was a significant decrease in systolic BP in response to 60 degrees head-up tilt. During isometric and dynamic exercise there was a smaller increase in systolic BP but a less marked effect on diastolic BP. Heart rate was unaffected either during free ambulation or during physiologic testing. The incidence of side effects was low. These results indicate that enalapril administered once daily may be an effective form of antihypertensive therapy. However, there is a group of patients who are unresponsive to treatment with converting enzyme inhibitors.

Adult↗

PubMed1984

Propranolol versus verapamil for the treatment of essential hypertension.

Recent reports have confirmed that slow calcium channel inhibitors have useful antihypertensive properties because they produce dilatation of the peripheral arterioles without reflex tachycardia. Their clinical place in the management of hypertension has yet to be clearly defined, and thus we have performed an open crossover trial to compare the 24-hour profiles of blood pressure reduction after chronic therapy with propranolol and verapamil. Nineteen patients were studied by continuous ambulatory intraarterial recording and the order of drug administration was decided by random allocation. Drug dosage was twice daily and titrated according to casual clinic pressures (propranolol, 40 to 240 mg twice a day; verapamil, 120 to 240 mg twice a day). Mean hourly blood pressure and heart rate values were obtained over a 24-hour cycle, and the responses to isometric and dynamic exercise were also examined. Both drugs were shown to produce a uniform and comparable reduction in blood pressure throughout the whole day, together with a reduction in heart rate, which was greater with propranolol. Comparable effects were also seen on the pressor responses to exercise. Both drugs were equally well tolerated and caused no patient withdrawals. We conclude that oral verapamil given twice daily showed a similar degree of efficacy to propranolol and provided 24-hour blood pressure control. This slow calcium channel inhibitor may be useful as initial therapy for hypertension, particularly for those patients in whom beta-adrenoreceptor blockers are contraindicated.

Adult↗

PubMed1984

Assessment of left ventricular function in coronary artery disease with the nuclear probe during intervention studies.

The nuclear probe was used for measuring left ventricular function in 11 normal subjects and the results compared with those using a digital gammacamera. The probe was then used to measure left ventricular function in patients with coronary artery disease during dynamic exercise and stress atrial pacing. The ability of the probe to detect changes induced by glyceryl trinitrate was also evaluated in separate parallel studies. In the 11 normal subjects there was a good correlation between the left ventricular ejection fraction measured by the gammacamera and the nuclear probe both at rest and during exercise. Exercise increased this value by at least 5% in all normal subjects during measurements with both the gammacamera and the nuclear probe. The mean (SD) difference was -0.3% (2.60) at rest and 2.3% (5.02) at peak exercise. Both exercise and pacing produced angina in the patient group and the mean (SEM) value fell from 52% (3.5) to 28% (2.6) and from 46% (5.1) to 34% (3.2) respectively. Glyceryl trinitrate prolonged the exercise and pacing times, and the corresponding falls in ejection fraction were significantly reduced. The non-imaging nuclear probe is a cheap and portable instrument capable of assessing left ventricular function in patients with cardiac disease. It is designed for high count rate acquisition over a short period of time and can thus provide both beat to beat and summated left ventricular time activity curves suitable for quantitative analysis. It therefore has important advantages in the clinical setting and during controlled interventions compared with the gammacameras.

Adult↗