[Class-I antiarrhythmic drugs]

Classification, mechanism of action, pharmacokinetic properties and clinical applications of class-I antiarrhythmic agents were summarized. Class-I drugs were subdivided into three groups, Ia, Ib, Ic. This subclassification is based on their action to modify the action potential duration. In the Cardiac Arrhythmia Suppression Trial (CAST), flecainide and encainide were associated with greater mortality than placebo in patients with non-life threatening arrhythmias. Results of CAST and other megatrials suggested that antiarrhythmic agents were unsafe in some groups of patients and the limitation of antiarrhythmic therapy. Proarrhythmia and combination therapy of antiarrhythmic agents were mentioned.

Effect of percutaneous transluminal coronary angioplasty on exercise ventilation in patients with coronary artery disease and normal left ventricular function

We evaluated the ventilatory response to exercise before and after percutaneous transluminal coronary angioplasty (PTCA) in 22 patients with coronary artery disease (CAD) and normal left ventricular systolic function to determine the effect of exercise-induced myocardial ischemia on the ventilatory response. Subjects performed a symptom-limited maximal ergometer exercise test in the sitting position. The ventilatory response was evaluated in terms of the slopes of minute ventilation (VE) and carbon dioxide production (VCO2) during exercise (slope 1 and slope 2, defined as below and above the respiratory compensation threshold, respectively). Slope 1 of the correlation between (VE) and (VCO2) was significantly greater in patients with CAD (27.3 +/- 2.6) than in the age-matched control group (23.7 +/- 2.6; p < 0.01). Slope 2 was also significantly greater in patients (41.0 +/- 4.8) than in the control group (29.7 +/- 2.9; p < 0.01). Slope 1 of the correlation between (VE) and (VCO2) decreased significantly in the 14 patients in whom PTCA was successful but did not decrease in the 8 patients in whom PTCA failed. Our results suggest that myocardial ischemia increases exercise ventilation in patients with CAD and normal left ventricular systolic function and that its effect is reversible.

Vasoconstriction by endothelin-1 in resistance and conduit portions of isolated human mesenteric arteries

Although physiological processes related to vascular function differ greatly between resistance arteries and conduit arteries, it is not known whether the effects of endothelin-1 on these arteries differ in humans. In the present study, the conduit portion and the resistance portion of isolated human mesenteric arteries were suspended in a Krebs-Ringer solution. Norepinephrine and endothelin-1 produced concentration-dependent contractions in both portions. The EC50 value of norepinephrine in the resistance portion (3.7 x 10(-7) M, n = 8) did not differ from that in the conduit portion (3.4 x 10(-7) M, n = 7). However, the EC50 value of endothelin-1 in the resistance portion (3.0 x 10(-9) M, n = 8) was significantly lower than that in the conduit portion (1.1 x 10(-8) M, n = 7, P < 0.05). Although the maximum response to norepinephrine in the resistance portion (calculated as the percentage of 50 mM KCl-induced contraction) did not differ from that in the conduit portion, the maximum response to endothelin-1 in the resistance portion was significantly greater than that in the conduit portion. These results indicate that endothelin-1 induces more potent constriction in resistance portion than in conduit portion in isolated human mesenteric arteries.

Endogenous endothelin-1 participates in the maintenance of cardiac function in rats with congestive heart failure. Marked increase in endothelin-1 production in the failing heart

BACKGROUND

Although it was demonstrated that circulating endothelin-1 (ET-1) levels are elevated in congestive heart failure (CHF), the production and roles of ET-1 in the failing heart are not known. We investigated the production of ET-1 in the heart and the density of myocardial ET receptors in rats with CHF. We also investigated the effects of intravenously infused BQ-123, an endothelin(A) (ETA) receptor antagonist, on both heart and myocardial contractility in rats with CHF.

METHODS AND RESULTS

We used the left coronary artery-ligated rat model of CHF (CHF rats). Three weeks after surgery, the rats developed CHF. Plasma ET-1 concentration was significantly higher in the CHF rats than in the sham-operated rats (P<.01). In the left ventricle, the expression prepro-ET-1 mRNA was markedly higher in the CHF rats than in the sham-operated rats. The peptide level of ET-1 in the left ventricle was also significantly higher in the CHF rats than in the sham-operated rats (500+/-41 versus 102+/-10 pg/g tissue, P<.01). Myocardial ET receptors were significantly higher in the CHF rats than in the sham-operated rats (243+/-20 versus 155+/-17 fmol/mg protein, P<.05). In the CHF rats, intravenous BQ-123 infusion (0.1 mg x kg(-1) x min(-1) for 120 minutes) significantly decreased both heart rate (P<.01) and LV+dP x dt(max) (P<.05) but not mean blood pressure. BQ-123 infusion did not affect these hemodynamic parameters in the sham-operated rats.

CONCLUSIONS

In the present study, we demonstrated that the production of ET-1 in the heart is markedly increased and that the density of myocardial ET receptors is significantly elevated in the CHF rats. Intravenous BQ-123 infusion significantly reduced both heart rate and LV+dP/dt(max) in the CHF rats but not in the sham-operated rats. Therefore, the ET receptor-mediated signal transduction system in the heart appears to be markedly stimulated in the CHF rats, and endogenous ET-1 may be involved in the maintenance of the cardiac function in these rats.

Long-term effects of doxazosin, an alpha 1-blocker, on serum lipids in hypertensive patients

Nowadays practical antihypertensive therapy involves not only simple normalization of blood pressure but also a reduction of the risks of cardiovascular disease. In this multicenter open-label study, the long-term effects of doxazosin, an alpha 1-adrenergic receptor blocker, on serum lipids were prospectively investigated in 253 patients with essential hypertension. They were treated with doxazosin for 1 year. The averaged the blood pressure was maintained at levels lower than 150/90 mmHg throughout 1 year, but heart rate did not increase. After 3 months of doxazosin therapy, total and low density lipoprotein-cholesterol levels in serum were significantly reduced by 3.3% and 3.4%, respectively, and these levels were maintained throughout the study period. This effect of doxazosin on serum lipids was especially prominent in patients with hypercholesterolemia. In addition, the lipid profile of these patients was favorably altered even when other antihypertensive drugs or lipid-lowering drugs had already been used or were used concurrently. These results constitute useful information for physicians who treat hypertension with alpha 1-blockers to reduce the overall risk of cardiovascular disease.

[Comparison of thrombolytic therapy and direct percutaneous transluminal coronary angioplasty for acute myocardial infarction: prospective multicenter trial at 16 clinical centers in Ibaraki prefecture TUGMI. Tsukuba University Group for Myocardial Infarction]

The efficacies of direct percutaneous transluminal coronary angioplasty (PTCA) and thrombolysis for the treatment of acute myocardial infarction were investigated in 80 patients treated within 12 hours of the onset of myocardial infarction by either PTCA (39 patients) or thrombolytic therapy (41 patients) followed by conservative care. The therapeutic approach was selected according to the treatment strategy at each of the 16 participating centers before the admission of the patients. The two treatment groups were closely matched in clinical characteristics except for the history of hypertension which occurred more in the thrombolysis group (22/39 vs 12/41, p = 0.026). The mean time before starting reperfusion therapy from the onset of symptoms was shorter in the thrombolysis group (2.3 +/- 1.5 vs 5.3 +/- 5.7 hours, p = 0.0001). Chest pain resolved more quickly in the PTCA group. Serial changes in the mean numbers of abnormal Q waves and mean values of the sum of elevated ST-segments on the electrocardiograms were similar in both groups. Serial changes of wall motion abnormality index on echocardiograms were similar in both groups. Coronary angiography after 4 weeks showed the thrombolysis group had greater residual luminal stenosis in the infarct-related artery. Left ventriculography after 4 weeks showed the PTCA group had better mean ejection fraction (68.1 +/- 11.2% vs 58.7 +/- 14.2%, p = 0.0263). Death (3/39 vs 1/41) and cardiac events (6/39 vs 6/41) after 4 weeks were similar in both groups. There was no significant difference in death and cardiac events between these two groups. However, the PTCA group had less severe residual luminal stenosis in the infarct-related artery and better left ventricular function after 4 weeks than the thrombolysis group.

Calcitonin gene-related peptide (CGRP) induces more potent vasorelaxation in the resistance portion than in the conduit portion of mesenteric arteries in humans

Although physiological processes related to vascular function differ greatly between resistance arteries and conduit arteries, it is not known whether the effects of calcitonin gene-related peptide (CGRP), a vasodilator neuropeptide, on these arteries differ in humans. In the present study, the conduit portion and the resistance portion of isolated human mesenteric arteries were suspended in a Krebs-Ringer solution. CGRP produced vasorelaxations in both portions. The EC50 values were very low both in the resistance portion (2.4 x 10(-9) M, n = 7) and in the conduit portion (2.2 x 10(-9) M, n = 7). The maximum response to CGRP in the resistance portion was significantly greater than that in the conduit portion (94.6 +/- 4.0% vs. 64.1 +/- 2.6% relaxation of methoxamine-induced precontraction, both n = 7, p < 0.01). These data suggest that CGRP is one of the most potent endogenous vasodilators in both the resistance portion and the conduit portion of the human mesenteric arteries, and that CGRP induces more potent vasorelaxation in the resistance portion than in the conduit portion of these arteries.

Resting asynchronous left ventricular contraction abnormality analyzed by a phase method in spastic angina pectoris

Quantitative phase analysis of equilibrium ventriculography was performed to study the character of left ventricular (LV) wall motion abnormalities in patients with spastic angina pectoris, who may have clinically and electrocardiographically silent ischemia combined with myocardial stunning, during rest and hyperventilation stress testing.

METHODS

Phase analysis of the left ventricle at rest was performed by equilibrium radionuclide ventriculography in 13 control subjects and 36 patients with spastic angina pectoris. First-pass methodology along with hyperventilation stress testing was performed to assess spasm occurrences. Phase analysis of equilibrium multigated blood-pool scintigrams was performed to evaluate LV asynchrony at rest.

RESULTS

The mean s.d. of LV phase distribution in the patients with variant and vasospastic angina was greater than that in the healthy control subjects (11.28 +/- 1.79 and 10.02 +/- 1.57 degrees versus 6.16 +/- 1.07 degrees). In addition, the mean s.d. of LV phase distribution in the variant angina group was greater than that in the vasospastic angina group. Furthermore, a linear correlation was found between the s.d. of LV phase distribution at rest and the percent decrease in ejection fraction during hyperventilation stress.

CONCLUSION

Asynchronous LV contraction without significant hypokinesis was detected at rest in spastic angina pectoris. The severity of this asynchronous contraction corresponded well with decreases in ejection fraction during hyperventilation stress testing. Thus, analysis of the s.d. of LV phase distribution at rest is expected to provide useful information regarding LV asynchrony in spastic angina pectoris.

Effects of L- and DL-carnitine on patients with impaired exercise tolerance

We designed this study to determine whether orally administered L- and DL-carnitine can improve exercise tolerance in a group of patients with exercise intolerance. Nineteen patients with cardiac disease were randomly divided into 2 groups, an L-carnitine treatment group (n = 9) and a DL-carnitine treatment group (n = 10). Eight additional age-matched patients served as an untreated control group. Subjects in both carnitine treatment groups underwent cardiopulmonary exercise testing on a cycle ergometer in order to determine peak exercise time, peak oxygen uptake (VO2), lactate threshold (LT) and ventilatory threshold (VT) before and after the oral administration of 900 mg/day of L- or DL-carnitine for 2 weeks. Basal values of peak exercise time, peak VO2, LT and VT did not differ significantly among the 3 groups. Peak exercise time and peak VO2 tended to be increased in the L-carnitine treatment group, and tended to be decreased in the DL-carnitine treatment group. Both LT and VT (ml/kg/min) were significantly improved (LT: from 9.7 +/- 0.6 to 10.8 +/- 1.0, p < 0.05; VT: from 9.8 +/- 0.8 to 11.8 +/- 1.9, p < 0.02) by the administration of L-carnitine, while LT was significantly decreased (from 11.0 +/- 2.0 to 9.6 +/- 1.2, p < 0.05) and VT tended to be decreased by the administration of DL-carnitine (from 11.6 +/- 2.0 to 10.8 +/- 2.4). In the untreated control group, no significant changes were observed in the values of exercise tolerance between the 2 series of exercise testings. In neither group did carnitine modify hemodynamic parameters at rest or during exercise. In conclusion, this study demonstrated that L-carnitine increases and DL-carnitine decreases exercise tolerance in patients with impaired exercise tolerance.

The diversity of left ventricular responses to isoproterenol and dibutyryl cyclic AMP infusion in patients with dilated cardiomyopathy

Sixteen patients with dilated cardiomyopathy were studied to define the abnormality of the beta-adrenergic pathway non-invasively, using echocardiographic left ventricular responses to isoproterenol (ISP; 0.02 microgram/kg/min) and dibutyryl cyclic AMP (DBcAMP; 0.1 mg/kg/min) infusion. The increase in fractional shortening induced by ISP (delta FS-ISP) was 9 +/- 6% and that by DBcAMP (delta FS-DBcAMP) was 7 +/- 3%. The patients could be divided into three groups according to their left ventricular response to each agent: Group A; normal response to ISP (delta FS-ISP > or = 11%), Group B-1; poor response to ISP but better response to DBcAMP (delta FS-ISP < 11%, delta FS-DBcAMP > or = 7%; damage to beta-receptors), and Group B-2; poor response to ISP and DBcAMP (delta FS-ISP < 11%, delta FS-DBcAMP < 7%; damage including post receptor levels). Seven patients were in Group A, four in Group B-1, and five in Group B-2. DCM patients had a diversity of left ventricular responses to ISP and DBcAMP, according to the site of damage in the beta-adrenergic pathway.

Response to isoproterenol as a prognostic indicator of evolution from hypertrophic cardiomyopathy to a phase resembling dilated cardiomyopathy

OBJECTIVES

We sought to assess whether isoproterenol stress echocardiography could detect in advance in which patients hypertrophic cardiomyopathy would progress to a phase resembling dilated cardiomyopathy.

BACKGROUND

In a few patients, hypertrophic cardiomyopathy has been reported to progress to a phase characterized by systolic dysfunction and left ventricular dilation, resembling dilated cardiomyopathy.

METHODS

Echocardiograms were recorded before and immediately after intravenous infusion of isoproterenol (0.02 microgram/kg body weight per min) for 5 min in 18 patients with typical hypertrophic cardiomyopathy (i.e., hypertrophied, hyperdynamic and nondilated) to determine the difference in fractional shortening. The patients were categorized into those with a good response (difference in fractional shortening > 7%, 14 patients) and those with a poor response (difference < or = 7%, 4 patients). Changes in left ventricular end-diastolic diameter and fractional shortening were evaluated by using serial echocardiography over an average follow-up period of 5.4 years.

RESULTS

In the good response group, neither end-diastolic diameter nor fractional shortening changed significantly during the follow-up period. In the poor response group, end-diastolic diameter significantly increased from a mean +/- SD of 41 +/- 5 to 53 +/- 5 mm (p < 0.05), and fractional shortening significantly decreased from 40 +/- 12% to 29 +/- 10% (p < 0.05). All patients in the poor response group showed a substantial decrease (> or = 5%) in fractional shortening and an increase (> or = 5 mm) in end-diastolic diameter. One patient developed congestive heart failure due to systolic dysfunction during the observation period.

CONCLUSIONS

The present study confirmed that impaired responses to isoproterenol infusion are related to future deterioration of left ventricular performance in patients with typical hypertrophic cardiomyopathy.

Malignant hyperthermia in a patient with Becker muscular dystrophy: dystrophin analysis and caffeine contracture study

We present a 17-year-old boy with Becker muscular dystrophy (BMD) who developed hyperthermia and heart failure after general anesthesia. He presented clinical features of malignant hyperthermia (MH), and had masseter spasm and elevated body temperature (38.7 degrees C) with very high serum CK activity (107,000 IUl-1). Dystrophin tests confirmed a clinical diagnosis of BMD in the patient, i.e. faint and patchy immunostaining pattern of skeletal muscle, truncated dystrophin protein and a deletion of exons 3 and 4 of the dystrophin gene. To inquire into the mechanism of MH associated in the patient, we tested caffeine contracture reaction by the skinned fiber method. We found an increased sensitivity to caffeine only in type 1 muscle fibers. The rate of Ca(2+)-induced Ca2+ release (CICR) was normal, suggesting that the mechanism of "MH" observed in our patient with BMD is not the same as that of classical MH. A possible mechanism might be related to derangements of the sarcoplasmic reticulum membrane in BMD, which sensitize the membrane to caffeine or other agents.

Exercise-induced rise in arterial potassium is enhanced in patients with impaired exercise tolerance

We assessed the changes in arterial potassium concentration during exercise and recovery in relation to exercise tolerance in patients with impaired exercise tolerance. Sixteen patients with cardiac disease were subjected to a cardiopulmonary exercise test on a cycle ergometer. Arterial potassium and lactate concentrations were measured every minute during and after exercise, and ventilatory threshold (VT) and lactate threshold (LT) were identified. Before exercise, arterial potassium concentration was 3.8 +/- 0.3 mEq/l. It increased to 4.1 +/- 0.3 mEq/l at LT (p < 0.002 versus at rest), to 4.2 +/- 0.3 mEq/l at VT, and to 4.8 +/- 0.5 mEq/l at peak exercise (p < 0.001 versus at LT, p < 0.001 versus at VT). At an exercise intensity equivalent to 30, 40, 50 or 60% of predicted maximum oxygen uptake, the increase in arterial potassium showed a negative and significant correlation with %LT (r = -0.62 approximately -0.72, p < 0.01 approximately 0.05) and %VT (r = -0.62 approximately -0.75, p < 0.001 approximately 0.05), where %LT and %VT represent the ratios of LT and VT to the predicted maximum oxygen uptake, respectively. There was a good correlation between the rate of fall in potassium concentration during recovery and its increase during exercise. It was concluded that in patients with impaired exercise tolerance, the greater the degree of exercise intolerance, the greater the increase in arterial potassium concentration during exercise, and the steeper the fall in potassium concentration during recovery. Because the rise in potassium concentration during exercise and its fall during recovery were greater when the exercise level exceeded the anaerobic threshold, exercise levels below the anaerobic threshold are recommended for patients with cardiac diseases.

Chronically decreased aortic distensibility causes deterioration of coronary perfusion during increased left ventricular contraction

OBJECTIVES

This study investigated the long-term effects of decreased aortic distensibility on the heart in relation to coronary perfusion.

BACKGROUND

Aortic distensibility is decreased in patients with atherosclerosis and hypertension and in the elderly. However, the effect of a long-term decrease in aortic distensibility on coronary perfusion has not been fully investigated.

METHODS

Twelve anesthetized dogs underwent thoracotomy and were allocated to two groups: Group I included six control dogs with a normal aorta; Group II included six dogs with decreased aortic distensibility produced by banding the descending aorta. After 4 to 6 weeks, the dogs had a second operation to measure coronary artery flow and transmural flow distribution. Because the effect of decreased aortic distensibility on coronary perfusion may be affected by ventricular contractility, measurements were performed at baseline and during increased ventricular contraction induced by isoproterenol infusion.

RESULTS

At baseline, arterial compliance was reduced by 35% in Group II, but there was no change in total mean arterial resistance. Hemodynamic variables, regional wall motion and coronary flow were also similar in both groups. However, during isoproterenol infusion, coronary flow increased more in Group II than in Group I (p < 0.01), and the coronary flow reserve ratio (maximal peak hyperemic flow divided by rest flow) decreased more in Group II than in Group I (mean [+/- SD] 1.9 +/- 0.4 vs. 2.4 +/- 0.3, p < 0.05). Moreover, although the transmural flow distribution was similar in the two groups at baseline, during isoproterenol infusion the endocardial flow increased less in Group II than in Group I (p < 0.05), and the endocardial/epicardial flow ratio was significantly decreased in Group II compared with Group I (mean [+/- SD] 0.70 +/- 0.18 vs. 0.99 +/- 0.22, p < 0.05). The subendocardial electrocardiogram showed ST segment elevation during isoproterenol infusion in Group II (p < 0.05) but not in Group I.

CONCLUSIONS

These results demonstrate that during increased ventricular contraction, chronically decreased aortic distensibility contributes to a further decrease in the coronary flow reserve ratio, impairs endocardial blood flow and may induce subendocardial ischemia even in the absence of coronary artery stenosis.

[A case of acute pandysautonomia and diffuse brain stem impairment associated with EB virus infection]

A 37-year-old woman with complaints of headache and nausea presented with temporary disturbance of consciousness, bulbar palsy and ataxic speech following flu-like symptoms. After the recovery of her consciousness, she developed orthostatic syncope and numbness all over the body. When she was admitted to our hospital two months later, she showed emaciation, diminished sweat production and butterfly-patch-like pigmentation. Neurologic examinations were remarkable for anisocoric pupils that sluggishly reacted to light, impaired left facial movements, bulbar palsy, numbness of the whole body, total loss of all tendon reflexes, incordination, ataxic gait and severe postural hypotension. Laboratory data included albuminocytogenic dissociation in cerebrospinal fluid, convergence nystagmus and dysmetria in electronystagmography, and right trigeminal paralysis in blink reflex. A sural nerve biopsy showed active axonal degeneration and severe loss of both myelinated and unmyelinated fibers. Examinations of autonomic nervous system disclosed diffuse impairment of sympathetic and parasympathetic postganglionic nerve. Based on these findings she was diagnosed as having acute pandysautonomia. High titer of serum EB virus antibody suggested that acute pandysautonomia and diffuse brainstem impairment may be related to EB virus infection.

Ventricular wall stress revisited. A keystone of cardiology

Wall stress has been used as one of the parameters of myocardial mechanics. The present review focuses on recently developed data on ventricular wall stress, especially in relation to other newly developed areas in cardiology. In hypertensive hearts, there is a broad continuous spectrum in the structural and functional changes: those with low wall stress (inappropriate hypertrophy), those with normal wall stress (appropriate hypertrophy) and those with high wall stress (inadequate hypertrophy). Among them, the responses to neurohumoral stimuli are various, and their clinical features and courses also varied. These differences in wall stress among the different categories of hypertensive hearts may be caused by the variable influences of non-mechanical factors, such as molecular, metabolic and neurohumoral ones. Wall stress is an essential determinant of myocardial oxygen consumption, and is also an important determinant of the myocardial contractile state and diastolic function. In contrast to excitation-contraction coupling, contraction-excitation feedback has been studied, suggesting the importance of wall stress regulating electrical phenomena. The interrelationship between mechanical factors (including wall stress) and non-mechanical factors (including molecular, metabolic, neurohumoral and genetic ones) has been investigated intensively. In conclusion, wall stress (or force on the myocardial cell) may be a keystone in cardiology, relating to each of the cardiac phenomena. If wall stress deviates from the normal range, even with compensatory mechanisms, severe cardiac events occur. The compensatory mechanisms for wall stress may act as a risk factor on the heart, especially when the wall stress remains outside the normal range.

Two cases of acute myocardial infarction associated with aplastic anemia during treatment with anabolic steroids

Thrombosis is a rare complication in patients with aplastic anemia because of the presence of coincidental thrombocytopenia. We have recently treated two cases, a 61-year-old male and a 59-year-old female, with acute myocardial infarction associated with aplastic anemia. Although their platelet counts were lower than normal in spite of treatment with anabolic steroids for aplastic anemia, the coronary angiographic findings strongly suggested coronary thrombosis in both cases. Anabolic steroids, which have been commonly used for the treatment of aplastic anemia, are a possible risk factor for coronary thrombosis because they have an accelerating effect on thrombus formation. We report two very rare but clinically important cases.

Increase in the chemically-induced differentiation of human leukemia cell lines by tubulin disruptors

The effect of various structural/functional tubulin disruptors (including colchicine-type disruptors, vinblastine, rhizoxin, maytansine, peptide-type disruptors, and taxol) on the chemically induced differentiation of human leukemia cell lines (HL-60 and K562) was examined. As differentiation-inducing agents, 12-O-tetradecanoylphorbol-13-acetate (TPA) was used for the differentiation of both HL-60 and K562 to monocyte/macrophages, retinoids were used for the differentiation of HL-60 to mature granulocytes, and hemin was used for the erythroid differentiation of K562. All the tubulin disruptors investigated increased the chemically-induced differentiation of HL-60 and K562 cell lines to the cognate mature cell types, regardless of the nature of the differentiation.

Endothelin receptor subtypes in human versus rabbit pulmonary arteries

We studied which endothelin (ET) receptor subtypes mediate ET-1-induced vasocontraction in the human pulmonary artery (PA) compared with the rabbit PA. ET-1 produced potent contraction in both human and rabbit isolated PAs. In human PA, ET-1-induced contraction was competitively antagonized by BQ-123 (an ETA receptor antagonist) with a pA2 value of 7.68. In rabbit PA, however, even a high concentration of BQ-123 (1 microM) did not affect the contraction. BQ-3020 (an ETB receptor agonist) produced potent contraction in rabbit PA but not in human PA. Binding assays of the membrane preparations showed that human and rabbit PAs contained ETA and ETB receptors in ratios of 93:7 and 23:77, respectively. These results suggest interspecies differences in the ET receptor subtypes that mediate ET-1-induced vasocontraction; ETA receptors are dominant in the human PA, whereas ETB receptors are dominant in the rabbit PA. Furthermore, the predominance of ETA receptors in human PA was supported by autoradiographical studies. If ET-1 acts as a physiological and/or pathophysiological vasocontractor in the human pulmonary circulation, an ETA receptor antagonist would function as a pulmonary vasodilator in humans.

[Characteristics of myocardial diseases in the elderly]

Myocardial diseases consist of cardiomyopathy of unknown origin and specific myocardial diseases of known origin. The former consists mainly of dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). In the latter, cardiac amyloidosis may be most frequently seen in the elderly. One hundred and twenty patients with cardiomyopathy were studied concerning their clinical courses. They were divided into 2 groups; i) young-middle-aged (Y) and ii) elderly (0). Group 1 was divided into 2 subgroups: 1a) followed up to an age less than 60 years old, and 1b) followed up to beyond age 60. In DCM, left ventricular posterior wall thickness and left atrial diameter increased significantly in the elderly. In HCM, young patients had obstructive type disease more frequently than the elderly. A history of mild hypertension was found more frequently in the middle-aged or elderly than in the young. Left ventricular end-diastolic diameter increased and left ventricular wall thickness decreased significantly in the elderly. Many patients with DCM usually die of congestive heart failure with ventricular arrhythmia, and those with HCM, both young or middle-aged, often die suddenly during sports activity. If there is an adaptive system, such as increased wall thickness in DCM or decreased wall thickness and increased diameter in HCM, which may contribute to the normalization of left ventricular wall stress, the patients might be able to survive to old age.