Thomas Lewis-the early years.
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History, 20th Century↗
Biomedical subjects
R W Harper
Publications and source records attributed to R W Harper.
Effects of verapamil on the electrophysiologic properties of the accessory pathway in patients with the Wolff-Parkinson-White syndrome.
The effects of intravenous verapamil on the electrophysiologic properties of the accessory pathway in 12 patients with symptomatic Wolff-Parkinson-White syndrome were studied using intracardiac electrical recordings. In 11 of the 12 patients it was possible to induce a reentrant supraventricular tachycardia with programmed atrial or ventricular pacing. After verapamil it was still possible to induce supraventricular tachycardia in 6 of the 11 patients; however, the mean cycle of length of the tachycardia increased from a control value of 330 +/- 20 ms (mean +/- standard error of mean) to 369 +/- 21 ms (p less than 0.05). Although verapamil had no significant effect on the anterograde refractory period of the accessory pathway as measured by the extrastimulus technique, it significantly increased maximal 1:1 atrioventricular (AV) conduction through the accessory pathway to incremental high rate atrial pacing in 10 of the 12 patients (control value 227 +/- 10 beats/min, value after verapamil 258 +/- 14 beats/min, p less than 0.001). In 4 patients in whom episodes of atrial fibrillation could be compared before and after verapamil, the drug decreased the average R-R interval from a control value of 327 +/- 27 ms to 282 +/- 28 ms (p less than 0.05) and decreased the shortest R-R interval between preexcited beats from a control value of 237 +/- 21 ms to 209 +/- 18 ms (p less than 0.05). It is concluded that in patients with symptomatic Wolff-Parkinson-White syndrome, verapamil may increase the ventricular response through the accessory pathway if atrial fibrillation occurs. This finding, which is of potential clinical significance, could not have been predicted from conventional anterograde refractory period estimations.
Adult↗
Adverse interaction between beta-adrenergic blocking drugs and verapamil--report of three cases.
Three patients with ischaemic heart disease developed profound cardiac failure, hypotension and bradycardia during combined therapy with verapamil and beta-adrenergic blocking drugs. This clinical picture resolved completely with cessation of the combined therapy. Baseline left ventricular function, assessed by cardiac catheterisation or nuclear angiography, was normal in two patients and only mildly reduced in the other. Simultaneously administration of beta-adrenergic blocking drugs and verapamil may result in profound adverse interactions and should only be administered with great caution.
Adrenergic beta-Antagonists↗
Right atrial thrombus simulating myxoma on M-mode echocardiography in a patient with pulmonary emboli.
Echoes from a right atrial mass in a patient with pulmonary embolism simulated a typical echocardiographic appearance of a right atrial myxoma. The patient was admitted with recurrent pulmonary emboli and had evidence of deep venous thrombosis on venography. M-mode echocardiography showed the appearance of a right atrial mass and right atrial angiography confirmed the presence of a mass prolapsing from right atrium into right ventricle. Subsequent 2-dimensional echocardiography and careful repeat M-mode echocardiography failed to demonstrate the mass suggesting embolisation to the lungs or lysis of the thrombus.
Adult↗
Radionuclide angiographic assessment of global and segmental left ventricular function at rest and during exercise after coronary artery bypass graft surgery.
Left ventricular ejection fraction (LVEF) was measured by radionuclide angiography at rest and during supine bicycle exercise before and 3 months after coronary artery bypass graft surgery (CABG) in 20 patients with chronic stable angina. The right anterior oblique gated first-pass technique was used to assess LVEF response to maximal exercise (Wmax), while the left anterior oblique equilibrium-gated technique was used to assess LVEF and relative LV volume changes during graded submaximal exercise. Mean LVEF was unchanged at rest after CABG by both the first-pass (60 +/- 12% vs 60 +/- 12%) and equilibrium-gated (61 +/- 13% vs 62 +/- 13%) measurements. At Wmax, mean first-pass LVEF was significantly higher postoperatively than preoperatively (63 +/- 17% vs 53 +/- 17%; p less than 0.01) with a higher Wmax (750 +/- 182 vs 590 +/- 202 kpm/min; p less than 0.001) and higher rate-pressure product (302 +/- 59 vs 222 +/- 57 units; p less than 0.001). Similarly, equilibrium-gated LVEF levels during graded exercise, using stepwise regression analysis, were significantly higher postoperatively than preoperatively (p less than 0.001); at the highest graded work load, they averaged 63 +/- 19% postoperatively and 53 +/- 17% preoperatively, with higher work loads (500 +/- 190 vs 417 +/- 155; p less than 0.05) and higher rate-pressure products (271 +/- 55 vs 207 +/- 53; p less than 0.001). The increase in exercise LVEF after surgery was due to a marked decrease in the ratio, relative to resting values, of counts-based end-systolic volumes during submaximal exercise (preoperatively 1.91 +/- 1.04; postoperatively 1.14 +/- 0.46; p less than 0.01). The five subjects in whom LVEF decreased significantly during exercise postoperatively all had one or more blocked or stenosed grafts. This study documents, by two independent radionuclide techniques, an improved LVEF during exercise at an increased maximal work capacity and rate-pressure product 3 months after successful CABG.
Adult↗
The use of radionuclide angiography in the non-invasive assessment of left atrial myxoma - A case report.
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Aged↗
The acute and chronic haemodynamic effects of prazosin in severe congestive cardiac failure.
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Blood Pressure↗
Isotope angiocardiography of the left ventricle.
Radionuclide imaging of the left ventricle is a recent innovative procedure requiring a gamma-camera interfaced to a computer. It has the advantages of being non-invasive and of allowing studies at rest and exercise. Left ventricular function may be assessed by viewing the images as an endless loop cine-display, or by quantitating the over-all and segmental functions. Validation studies comparing the technique with standard contrast angiograms have confirmed its reliability. Clinical studies have been undertaken in normal volunteers, and in patients. The technique will have increasing application in assessing the aetiology of chest pain, in selection of patients for cardiac surgery, and in determining the effects of interventions, such as drug therapy or coronary artery bypass surgery, on ventricular performance.
Adult↗
The radionuclide assessment of left ventricular function using graded exercise in normal subjects.
In 20 normal volunteers, two minute equilibrium gated blood pool scanning (GBPS) was used to assess left ventricular function during rest and three stages of graded supine exercise on a bicycle ergometer. The three work loads were individualised for each subject from a previously performed exercise test and corresponded to mild, moderate and severe stress. The short imaging time was validated against standard GBPS. With exercise all subjects increased their left ventricular ejection fraction and in the majority, most of this rise occurred with the lowest work load. This change was predominantly due to a marked fall in end-systolic volume. The end-diastolic volume initially fell, then at peak exercise returned to baseline values. The major change in stroke volume occurred at peak exercise.
Adult↗
The incidence and pattern of angina prior to acute myocardial infarction: a study of 577 cases.
In order to determine the incidence and pattern of angina as a premonitory symptom of acute myocardial infarction, 577 consecutive patients with acute myocardial infarction were questioned shortly after hospital admission about the presence and pattern of chest pain prior to onset of infarction, with particular emphasis on the month prior to infarction. Two hundred and seventy-six patients (48 per cent) had no angina before infarction (Group I), whereas 301 (52 per cent) did. One hundred and seventy-nine patients (31 per cent) had a history of chronic angina, and of these, 75 had no change in the pattern of angina prior to infarction (Group II) while 104 noticed worsening of their symptoms in the month prior to infarction (Group III). One hundred and twenty-two patients (21 per cent) had new onset angina in the month prior to infarction (Group IV). The number of patients with unstable angina prior to infarction (Groups III and IV) was therefore 226 or 39 per cent of the total series. In patients with unstable angina, the increase in severity of symptoms or the development of new onset angina occurred within a period of 1 week or less in 69 per cent. Patients with a history of previous infarction or chronic angina had a higher incidence of unstable angina prior to infarction than patients without such a history (p less than 0.05). Patients with prior angina (Groups II, III, and IV) had a higher incidence of subendocardial infarction than patients without angina (p less than 0.05). The hospital mortality rate in the four groups did not differ significantly.
Age Factors↗
Effect of mexiletine on monophasic action potentials recorded from the right ventricle in man.
The effect of mexiletine, a new antiarrhythmic agent, on ventricular refractoriness and monophasic action potentials recorded from the right ventricle was studied in nine subjects. The effective refractory period of the right ventricle was determined by the extra stimulus technique using a pacing electrode situated at the right ventricular apex. Following this determination the right ventricular apex was paced at a constant cycle length and premature stimuli were introduced starting at a coupling interval of 2 ms greater than the ventricular refractory period and then at progressively increasing coupling intervals of 5 ms increments. Simultaneous recordings of monophasic action potentials of both the regular paced beats and the induced premature beats were made using a specially designed suction electrode catheter. The monophasic action potential durations were measured at 50% and 90% repolarisation. All these control measurements were repeated after an intravenous dose of 2 mg.kg-1 body wt. of mexiletine. The results showed that mexiletine did not significantly change the effective ventricular refractory period nor did it alter the monophasic action potential duration of the regular paced beat. The drug did, however, significantly prolong the monophasic action potential duration of the early induced premature beats and it is possible that this property of the drug may be related to its antiarrhythmic activity.
Action Potentials↗
Effect of mexiletine on conduction of premature ventricular beats in man: a study using monophasic action potential recordings from the right ventricle.
Ventricular conduction intervals between a stimulating pacemaker electrode at the right ventricular apex and an impulse detecting monophasic action potential electrode at the right ventricular septum were measured in nine subjects. The right ventricle was paced at a constant rate and programmed premature ventricular stimuli were introduced after every eighth paced beat beginning at the refractory period. The ventricular conduction intervals were measured from the pacemaker artefact to the onset of depolarisation of the MAP recording. In the control recordings a short period of prolonged (subnormal) conduction lasting for 5 to 26 ms after the refractory period was present in six of the nine subjects. In eight subjects a period of 'supernormal' conduction lasting from 50 to 180 ms was present. The effect of mexiletine was to increase the subnormal conduction and to abolish the supernormal conduction. It is concluded that a small degree of supernormal conduction occurs in the normal human ventricle possibly as a result of phase 4 depolarisation of cells of the specialised conducting system.
Action Potentials↗
Patterns of haemodynamic alteration during left ventricular ischaemia in man. Relation to angiographic extent of coronary artery disease.
Haemodynamic changes produced by rapid atrial pacing (60 patients, 52 of whom developed angina) or in association with spontaneous angina (32 patients) were measured in 92 patients with angiographic coronary artery disease. The extent of coronary artery disease was scored by the jeopardy score system (range 0 to 12). The haemodynamic changes induced by ischaemia occurred in 3 patterns: pattern I, no change in filling pressure or in mean systemic arterial pressure; pattern II, a rise in filling pressure and a rise in mean systemic arterial pressure; pattern III, a rise in filling pressure, but no significant change or a fall in mean systemic arterial pressure. In patients who had a pattern II or a pattern III response to ischaemia, the change in mean systemic arterial pressure was linearly related to the corresponding change in cardiac output. The likelihood of a patient showing a given pattern of ischaemia-induced haemodynamic change was related to the extent of coronary artery disease; of 22 patients with jeopardy scores of 2 or 4, 91% exhibited pattern I, 9% pattern II, and none pattern III; of 39 patients with jeopardy scores of 6 or 8, 40% exhibited pattern I, 22% pattern II, and 38% pattern III; of 31 patients with jeopardy scores of 10 or 12, 12% exhibited pattern I, 10% pattern II, and 78% pattern III (P less than 0.01). Among the 54 patients in whom serial cardiac output determinations were available, a decline of the left ventricular function curve during ischaemia was demonstrable in 8% of those with a pattern I response, in 54% of those with a pattern II response, and in 90% of those with a pattern III response (P less than 0.01). The pattern of response was unrelated to resting angiographic left ventricular ejection fraction, whether ST segments became elevated or depressed, or whether ischaemia was pacing-induced or spontaneous. These results suggest that the haemodynamic response to ischaemia is determined by the fraction of the left ventricle that becomes dysfunctional during ischaemia.
Blood Pressure↗
Severity of coronary atherosclerosis related to lipoprotein concentration.
The influence of individual lipoproteins on the severity of coronary atherosclerosis was studied in 41 patients undergoing coronary angiography. The extent of athero-sclerosis was quantified by a coronary atherosclerosis score (CAS) based on the number and severity of lesions in eight proximal segments of the coronary circulation. The concentration of high-density lipoprotein (HDL) showed a strong inverse association with CAS, which was independent of the effects of age and other lipoproteins. On multivariate analysis concentrations of other lipids--namely, total plasma cholesterol, low-density lipoprotein (LDL) cholesterol, and the combined effect of LDL cholesterol plus very-low-density lipoprotein triglyceride--showed direct, significant correlations with CAS, but these were weaker than that of HDL. This study shows that concentrations of several circulating lipoproteins are related to the severity of coronary atherosclerosis, HDL having an apparent retarding effect. These findings may partly explain the influence of lipoproteins on the development of clinical coronary heart disease.
Adult↗
Mexiletine effect on monophasic action potential (MAP) of right ventricle in man.
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Action Potentials↗
Early intraaortic balloon pumping for anterior myocardial infarction without shock.
Eleven patients with anterior myocardial infarction less than six hours old underwent intraaortic balloon pumping (IABP) in an attempt to control injury. Direct hemodynamic measurements excluded shock. Response to therapy was judged individually by comparison to a one-hour pretreatment period. There was no parallel control group. Five patients responded with an 84% fall in ST elevation in one hour, with preservation of precordial R waves and good ventricular function. In contrast, six patients responded poorly, with a 40% fall in ST elevation in one hour, Q wave development and poorer residual left ventricular function. Coronary angiography demonstrated a significant correlation between response and presence or absence of complete left anterior descending coronary artery occlusion. Early use of IABP in anterior myocardial infarction may interrupt injury, though in this series only in cases with residual left anterior descending patency.
Adult↗
The effect of mexiletine on the electrophysical properties of the intact human heart.
The effect of an intravenous dose of mexiletine, a new anti-arrhythmic agent, on the electrophysiological properties of the intact human heart was studied in ten subjects with no evidence of cardiovascular disease. Mexiletine produced no significant changes in the sinus node recovery time, the corrected sinus node recovery time or in the atrial, atrio-ventricular and ventricular effective refractory periods. In addition mexiletine had no significant effect on proximal atrioventricular conduction. The drug did, however, prolong atrio-ventricular conduction distal to the bundle of His in all ten subjects by an average of 6 msec. This change was statistically significant (P less than 0.01). The drug is recommended to be used with caution in patients with conduction disturbances.
Adult↗
Successful surgical resection of a chronic false aneurysm of the left ventricle.
The case of a patient with a chronic false aneurysm of the left ventricle diagnosed three years after a documented myocardial infarction is reported. The patient presented with a mass seen on the chest x-ray examination. The correct diagnosis was made by ventriculography and the aneurysm was successfully resected.
Chronic Disease↗