Regional thallium-201 washout and myocardial hypertrophy in hypertrophic cardiomyopathy and its relation to exertional chest pain

Electrophysiological mechanisms underlying T wave pseudonormalisation on stress ECGs in hypertrophic cardiomyopathy

BACKGROUND

Pseudonormal T waves may be detected on stress electrocardiograms (ECGs) in hypertrophic cardiomyopathy (HCM). Either myocardial ischaemia or purely exercise-induced changes have been hypothesised to contribute to this phenomenon, but the precise electrophysiological mechanisms remain unknown.

METHODS

Computational models of human HCM ventricles (n = 20) with apical and asymmetric septal hypertrophy phenotypes with variable severities of repolarisation impairment were used to investigate the effects of acute myocardial ischaemia on ECGs with T wave inversions at baseline. Virtual 12-lead ECGs were derived from a total of 520 biventricular simulations, for cases with regionally ischaemic K+ accumulation in hypertrophied segments, global exercise-induced serum K+ increases, and/or increased pacing frequency, to analyse effects on ECG biomarkers including ST segments, T wave amplitudes, and QT intervals.

RESULTS

Regional ischaemic K+ accumulation had a greater impact on T wave pseudonormalisation than exercise-induced serum K+ increases, due to larger reductions in repolarisation gradients. Increases in serum K+ and pacing rate partially corrected T waves in some anatomical and electrophysiological phenotypes. T wave morphology was more sensitive than ST segment elevation to regional K+ increases, suggesting that T wave pseudonormalisation may sometimes be an early, or the only, ECG feature of myocardial ischaemia in HCM.

CONCLUSIONS

Ischaemia-induced T wave pseudonormalisation can occur on stress ECG testing in HCM before significant ST segment changes. Some anatomical and electrophysiological phenotypes may enable T wave pseudonormalisation due to exercise-induced increased serum K+ and pacing rate. Consideration of dynamic T wave abnormalities could improve the detection of myocardial ischaemia in HCM.

Mechanisms and prognostic impact of myocardial ischaemia in hypertrophic cardiomyopathy

Despite the progress made in risk stratification, sudden cardiac death and heart failure remain dreaded complications for hypertrophic cardiomyopathy (HCM) patients. Myocardial ischaemia is widely acknowledged as a contributor to cardiovascular events, but the assessment of ischaemia is not yet included in HCM clinical guidelines. This review aims to evaluate the HCM-specific pro-ischaemic mechanisms and the potential prognostic value of imaging for myocardial ischaemia in HCM. A literature review was performed using PubMed to identify studies with non-invasive imaging of ischaemia (cardiovascular magnetic resonance, echocardiography, and nuclear imaging) in HCM, prioritising studies published after the last major review in 2009. Other studies, including invasive ischaemia assessment and post-mortem histology, were also considered for mechanistic or prognostic relevance. Pro-ischaemic mechanisms in HCM reviewed included the effects of sarcomeric mutations, microvascular remodelling, hypertrophy, extravascular compressive forces and left ventricular outflow tract obstruction. The relationship between ischaemia and fibrosis was re-appraised by considering segment-wise analyses in multimodal imaging studies. The prognostic significance of myocardial ischaemia in HCM was evaluated using longitudinal studies with composite endpoints, and reports of ischaemia-arrhythmia associations were further considered. The high prevalence of ischaemia in HCM is explained by several micro- and macrostructural pathological features, alongside mutation-associated energetic impairment. Ischaemia on imaging identifies a subgroup of HCM patients at higher risk of adverse cardiovascular outcomes. Ischaemic HCM phenotypes are a high-risk subgroup associated with more advanced left ventricular remodelling, but further studies are required to evaluate the independent prognostic value of non-invasive imaging for ischaemia.

Endothelial dysfunction, subangiographic atheroma, and unstable symptoms in patients with chest pain and normal coronary arteriograms

BACKGROUND

Patients with chest pain and normal coronary arteriograms (CPNA) may present with unstable symptoms and other evidence of ischemia during clinical follow-up. Although repeat angiography usually proves negative, functional assessment of coronary vasomotor abnormalities may provide additional pathophysiologic information.

HYPOTHESIS

The study was undertaken to evaluate the relationship between endothelial dysfunction and subangiographic atheroma in patients with CPNA undergoing repeat angiography because of unstable symptoms.

METHODS

We investigated nine patients with CPNA (8 women, mean age 57 +/- 9 years) undergoing repeat angiography because of unstable anginal symptoms. After normal angiography, simultaneous coronary epicardial and microvascular vasomotor responses to intracoronary vasodilators [acetylcholine (10(-6) M), adenosine (18 micrograms) and nitroglycerin (300 micrograms)] were investigated in the left anterior descending artery using quantitative angiography and Doppler flow measurements. The presence of subangiographic atheroma was assessed by intravascular ultrasound.

RESULTS

Three patients demonstrated proximal and distal epicardial vasoconstriction and a reduction in coronary flow in response to acetylcholine, indicating concordant epicardial and microvascular endothelial dysfunction. These changes were associated with chest pain and ischemic electrocardiographic changes in two patients. None of the remaining patients suffered chest pain in response to intracoronary acetylcholine. Six patients had significant subangiographic disease (intimal thickness > 0.3 mm) on intravascular ultrasound imaging, and multivariate analysis indicated a significant relationship (R2 = 0.89, overall p = 0.001) between the extent of subangiographic disease and both plasma cholesterol concentration and hypertensive history. No significant relationship was demonstrated between endothelial dysfunction and the extent of subangiographic disease.

CONCLUSION

Concordant epicardial and microvascular endothelial dysfunction may be pathophysiologically and clinically significant in unstable patients with CPNA but does not appear to be directly related to the extent of subangiographic atheroma.

Echocardiographic predictors of severe heart failure symptoms in hypertrophic cardiomyopathy patients with sinus rhythm

Background

Symptoms in hypertrophic cardiomyopathy (HC) appear to be caused by diastolic dysfunction, myocardial ischemia, left ventricle (LV) outflow obstruction, and atrial fibrillation. However, clinical deterioration and severe heart failure symptoms can be observed in patients without any of these factors. Thus, the aim of this study is to determine the echocardiographic predictors of severe heart failure symptoms in patients with HC.

Methods and results

86 HC patients were compared according to symptomatic status. Patients with severe heart failure symptoms were older, preponderantly female, had more often LV outflow obstruction and mitral regurgitation, longer E wave deceleration time (EDt), higher E/Ea ratios and lower LV tissue Doppler (TD) velocities when compared to rest of the patients. LV outflow obstruction (r = 0.43, R² = 0.19, p < 0.0001), LV lateral mitral annular systolic TD velocity (LMSa) (r = 0.51, R² = 0.26, p < 0.006) and EDt (r = 0.55, R² = 0.30, p < 0.027) were found to be the independent predictors for severe heart failure symptoms in forward stepwise regression.

Conclusion

In HCM patients with sinus rhythm and normal LV systolic function, LMSa, EDt and LV outflow obstruction are independent predictors of heart failure symptoms. Diastolic dysfunction determined with EDt, occult systolic dysfunction which is detected with TD analysis, and afterload increase as result of LV outflow obstruction seem to be the main echocardiographic factors affecting symptomatic status in HCM patients with sinus rhythm and normal systolic function.

Prognostic utility of single-photon emission computed tomography in adult patients with hypertrophic cardiomyopathy

BACKGROUND

Data derived from stress myocardial perfusion imaging (MPI) carry prognostic significance in young patients with hypertrophic cardiomyopathy (HCM), but there are limited data on the utility of stress MPI in patients with HCM who are older. This study examined the prognostic significance of stress MPI in an adult population of patients with HCM.

METHODS

We examined 158 patients with HCM (aged 60 +/- 16 years, 61% men) who underwent exercise or pharmacologic stress MPI. Summed stress score (SSS, normal = 56) and summed reversibility scores were calculated for each patient. Follow-up was complete in 157 (99%) patients at a median duration of 5.2 years.

RESULTS

Normal single-photon emission computed tomography (SPECT) images were present in 38% of the population. Summed stress score (P = .01) and summed reversibility score (P = .03) were both significantly associated with cardiovascular death. Survival at 10 years was significantly better in those with normal versus abnormal SPECT (89% vs 67%, P = .04). Ten-year survival also was better in those without versus those with ischemia (90% vs 64%, P = .02). Five-year survival could be stratified by SSS risk categories: low risk (SSS > or = 53), 97%; intermediate risk (SSS = 48-52), 94%; and high risk (SSS < or = 47), 79% (P = .04). Bivariate models of SSS and other significant covariates supported an independent relation of SSS to cardiovascular death.

CONCLUSIONS

In an older population of patients with HCM referred for SPECT imaging, abnormal stress MPI identifies those at increased risk of cardiovascular death.

Brachial artery flow-mediated dilation and myocardial perfusion in patients with cardiac syndrome X

We assessed the relation between systemic endothelial dysfunction abnormalities (brachial artery flow-mediated dilation) and myocardial perfusion abnormalities (single-photon emission computed tomography) in 41 patients who had cardiac syndrome X. Eighteen patients had normal perfusion scans and 18 had transient perfusion defects. Reverse redistribution was found in 5 patients. Patients who had myocardial perfusion defects had significantly lower flow-mediated dilation values (1.8%) than patients who had normal single-photon emission computed tomograms (3.9%, p = 0.012). Preserved systemic endothelial function appears to rule out the occurrence of transient single-photon emission computed tomographic defects in patients who have cardiac syndrome X.

Myocardial thallium defects in apical hypertrophic cardiomyopathy are associated with a benign prognosis. Thallium defects in apical hypertrophy

BACKGROUND

We investigated whether myocardial thallium-201 defects in patients with apical hypertrophic cardiomyopathy are associated with an unfavorable clinical outcome, and additionally compared the presence of defects to echocardiography and angiography findings.

METHODS

Dipyridamole thallium-201 single photon emission tomography was performed in 26 apical hypertrophic cardiomyopathy patients, aged 41-78 (22 men, 6 women). Patients with or without perfusion defects were compared for echocardiographic measurements of wall thickness, chamber dimensions, and fractional shortening. Twelve patients underwent coronary angiography. The occurrence of cardiac events was evaluated during clinical follow-up for a mean period of 4.3 +/- 1.9 years (range: 1.0-7.0 year).

RESULTS

Thirteen patients (50%) showed perfusion defects, which were predominantly reversible (fixed in 1) and mostly apical (9 of 13). Patients with and without defects did not differ in symptoms, EKG findings, echocardiographic morphology or fractional shortening (41 +/- 4 vs. 41 +/- 7%). Coronary angiography was normal in all patients in whom it was performed (nine with and three without defects). During follow-up, there were no deaths or myocardial infarction. Of the defect positive group, one case developed paroxysmal supraventricular tachycardia, and another had a cerebrovascular accident. Of the defect negative group, one case developed sick sinus syndrome, while another had a hospital admission for anginal pain.

CONCLUSIONS

While reversible thallium defects in the absence of coronary artery disease occur frequently in patients with apical hypertrophic cardiomyopathy, the prognosis remains benign despite the presence of ischemia and there is no evidence for an association with adverse patient outcome.

Approach to the patient with chest pain and nonobstructive coronary artery disease

Patients with chest pain and nonobstructive coronary artery disease (NOCAD) utilize a significant part of our health care resources. Their diagnosis and treatment can often be difficult and time consuming. A simple classification system and stepwise diagnostic approach may help to reduce unnecessary testing. Also, utilization of a chest pain clinic may be beneficial for these patients.

Septal stunning by dipyridamole stress shown on quantitative gated perfusion SPECT in a child with hypertrophic cardiomyopathy

PURPOSE

Myocardial ischemia is an important problem in hypertrophic cardiomyopathy. Stunning is an important mechanism in progressive dysfunction of the ischemic myocardium. In this report, the authors found prolonged myocardial stunning in a child with hypertrophic cardiomyopathy that was induced by dipyridamole stress on quantitative gated SPECT.

MATERIALS AND METHODS

A 6-year-old boy with septal hypertrophy underwent rest and dipyridamole stress gated myocardial SPECT. Software was used to quantify automatically segmental perfusion and function at rest and after stress.

RESULTS

Perfusion imaging showed a reversible perfusion decrease in the hypertrophic septum. Cine-gated imaging of the septum showed dyskinesia and a severe abnormality of systolic thickening during the poststress period, whereas it showed nearly complete recovery at rest. Quantified regional perfusion and function indices also showed this perfusion decrease and myocardial dysfunction after dipyridamole stress.

CONCLUSION

In a child with hypertrophic cardiomyopathy, myocardial stunning was induced by dipyridamole stress, in accordance with decreased perfusion reserve.

[Myocardial SPET in hypertrophic cardiomyopathy]

INTRODUCTION AND OBJECTIVES

The aim of this study was to evaluate the diagnostic accuracy of myocardial SPET in patients with hypertrophic cardiomyopathy (HC).

PATIENTS AND METHODS

One hundred and six consecutive patients (aged 53 +/- 12 years, 50 women, 66 with dynamic obstruction) with an echocardiographic diagnosis of HC were studied with exercise-rest myocardial SPET with 99mTc-tetrofosmin. Forty-six (43%) of these patients had chest pain and in 31 (29%) a coronary angiography was performed. Fifty-six per cent of the patients were treated with beta-blockers and 23% with verapamil.

RESULTS

Angina during the exercise test was observed in only 8% of the patients. Perfusion defects were observed in 35% of the patients. Only 8 (26%) out of the 31 patients with angiography had coronary artery disease (stenosis > 50%). When fixed and reversible defects were considered as positive, the sensitivity was 50%, the specificity was 65%, the positive predictive value was 33% and the negative predictive value was 79%.

CONCLUSIONS

Myocardial perfusion defects can be observed in more than one third of medically treated patients with HC. Only a quarter of catheterized patients, even with chest pain, have associated coronary artery disease. The accuracy of SPET for the diagnosis of coronary artery disease in hypertrophic cardiomyopathy is low. Thus, the value of this technique is limited in these patients.

Negative stress echocardiographic responses in normotensive and hypertensive patients with angina pectoris, positive exercise stress testing, and normal coronary arteriograms

OBJECTIVES

To systematically compare the results of dobutamine stress echocardiography in matched groups of hypertensive and normotensive patients with anginal chest pain and normal coronary arteriograms (CPNA).

SETTING

University hospital.

SUBJECTS

33 patients with exertional anginal chest pain, a positive exercise stress ECG, and a completely normal coronary arteriogram; 17 had a history of systemic hypertension (14 women; mean (SD) age 57 (6) years), and 16 had no hypertensive history (12 women; age 54 (9) years).

METHODS

Ambulatory ECG monitoring, dobutamine stress echocardiography, and thallium-201 single photon emission computed tomography (SPECT) were performed in all subjects.

RESULTS

All patients had normal left ventricular systolic function at rest and none fulfilled the criteria for ventricular hypertrophy. Eight normotensive patients and 10 hypertensive patients had perfusion abnormalities on thallium SPECT (p = 0.61). Dobutamine infusion reproduced anginal pain in seven normotensive and seven hypertensive patients (p = 0.88). ST segment depression was also recorded in eight normotensive patients and seven hypertensive patients (p = 0. 61). No patient in either group developed regional wall motion abnormalities during dobutamine stress echocardiography.

CONCLUSIONS

Neither hypertensive nor normotensive CPNA patients developed regional wall motion abnormalities during dobutamine stress echocardiography, despite the high prevalence of scintigraphic perfusion defects in both groups and the presence of chest pain and ST segment depression. Thus myocardial ischaemia was not present in either group, or else dobutamine stress echocardiography is insensitive to ischaemia caused by microvascular dysfunction.

Coronary vasodilator reserve is impaired in patients with hypertrophic cardiomyopathy and left ventricular dysfunction

BACKGROUND

We tested the hypothesis that a reduced delivery of blood to the myocardium is involved in the development of systolic dysfunction of patients with hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Eighty-four patients with HCM (62 men, age 43 +/- 12 years) were studied. Left ventricular dimensions and function (fractional shortening) were evaluated by 2-dimensional echocardiography. Myocardial blood flow (MBF) was measured by N13 -ammonia or O15 -water and positron emission tomography at baseline and after dipyridamole; coronary vasodilator reserve (CVR) was calculated as dipyridamole/baseline MBF. Patients with HCM in advanced New York Heart Association (NYHA) classes had lower dipyridamole MBF (NYHA class I = 1.57 +/- 0.64 vs class II = 1.52 +/- 0.58 vs class III = 0.96 +/- 0.32 mL/min per gram; analysis of variance, P <.05) and CVR (NYHA class I = 1.93 +/- 0.64 vs class II = 1.69 +/- 0.54 vs class III = 1.40 +/- 0.43; analysis of variance, P <.05). A positive linear correlation between fractional shortening and dipyridamole MBF was demonstrated (R = 0.23, P <.05), and patients with abnormal fractional shortening had lower dipyridamole MBF (1.07 +/- 0.43 vs 1.58 +/- 0.62 mL/min per gram, P <.01).

CONCLUSIONS

Systolic dysfunction in HCM may be caused by a more severe alteration of the coronary vasodilator capacity.

Comparison of the functional significance of left ventricular hypertrophy in hypertrophic cardiomyopathy and glycogenosis type III

A comparison of blood pressure response with exercise stress, thallium scintigraphy, and 24-hour electrocardiographic monitoring between 5 patients with left ventricular hypertrophy associated with glycogen storage disease type III and 10 matched patients with hypertrophic cardiomyopathy revealed normal results in the former group. These data highlight the importance of the etiology of left ventricular hypertrophy before the application of risk stratification.

Impaired response of left ventricular relaxation to exercise-induced adrenergic stimulation in patients with hypertrophic cardiomyopathy

OBJECTIVES

We investigated the effect of adrenergic stimulation on left ventricular relaxation in patients with hypertrophic cardiomyopathy.

BACKGROUND

Exercise-induced decreases in acceleration of left ventricular relaxation have been observed in patients with hypertrophic cardiomyopathy. However, data on sequential changes in left ventricular relaxation during exercise are limited.

METHODS

We measured right (fluid filled) and left (high fidelity micromanometer) ventricular pressures during moderate supine ergometer exercise and during rapid right atrial pacing in four groups of patients: 9 with severe hypertrophic cardiomyopathy, 9 with moderate hypertrophic cardiomyopathy, 10 with hypertension and moderate hypertrophy and 5 control subjects.

RESULTS

There was a curvilinear relation between the time constant of relaxation (tau) and heart rate in all groups during exercise. There was no difference in the slope of this relation between the two hypertrophic cardiomyopathy subgroups. Although the slope of this relation between tau and heart rate was steeper in the hypertensive than the moderate hypertrophic cardiomyopathy group (p < 0.001, analysis of covariance), the decrease in tau during right atrial pacing was similar in both groups. There were no significant differences in plasma levels of catecholamines at rest or at peak exercise among groups or in maximal heart rate during pacing.

CONCLUSIONS

Pacing-induced changes in tau in hypertrophic cardiomyopathy were similar to those in hypertensive hypertrophy, but remarkable decrease in exercise-induced acceleration of tau were observed only in hypertrophic cardiomyopathy. Our results may indicate a depressed left ventricular relaxation response to exercise-induced adrenergic stimulation in hypertrophic cardiomyopathy.

Effects of permanent dual chamber pacing on myocardial perfusion in symptomatic hypertrophic cardiomyopathy

OBJECTIVE

Angina and the presence of myocardial ischaemia are common in hypertrophic cardiomyopathy. Dual chamber pacing results in clinical improvement in these patients. This study evaluates the effects of permanent dual chamber pacing on absolute regional myocardial perfusion and perfusion reserve.

SETTING

University hospital.

PATIENTS AND DESIGN

Six patients with hypertrophic cardiomyopathy and severe symptoms of angina received a dual chamber pacemaker. Absolute myocardial regional perfusion and perfusion reserve (dipyridamole 0.56 mg/kg) were measured by dynamic positron emission tomography with 13N-ammonia both during sinus rhythm and 3 months after pacemaker insertion. Results were compared with those from 28 healthy volunteers.

RESULTS

Pacing resulted in a reduction of anginal complaints and a reduction in intraventricular pressure gradient from 65 (SD 30) mm Hg to 19 (10) mm Hg. During sinus rhythm, baseline perfusion was higher in patients with hypertrophic cardiomyopathy than controls (184 (31) v 106 (26) ml/min/100 g, P < 0.01), and perfusion reserve was lower (1.6 (0.4) v 2.8 (1.0), P < 0.05). During pacing myocardial perfusion decreased to 130 (27) ml/min/100 g (P < 0.05), with variable responses in terms of perfusion reserve. Pacing caused a redistribution of myocardial stress perfusion and perfusion reserve. The coefficient of regional variation of myocardial stress perfusion decreased from 19.7 (7.0)% to 14.6 (3.9)% during pacing (12.9 (3.8)% in controls, P < 0.01). The coefficient of regional variation of perfusion reserve decreased from 16.7 (6.6)% to 11.4 (2.6)% during pacing (9.8 (4.1)% in controls, P < 0.01).

CONCLUSIONS

Pacing caused a decrease of resting left ventricular myocardial blood flow and blood flow during pharmacologically induced coronary vasodilatation. Although global perfusion reserve remained unchanged, myocardial perfusion reserve became more homogeneously distributed.

Coronary flow reserve and exercise capacity in hypertrophic cardiomyopathy

The aim of this study was to evaluate the relation of coronary flow velocity (CFV) and coronary flow reserve (CFR) to exercise capacity in ten verapamil-treated patients with hypertrophic cardiomyopathy (HC). Using Doppler transesophageal echocardiography, we assessed diastolic CFV in the proximal left anterior descending coronary artery at baseline and after administering 0.56 mg/kg intravenous dipyridamole. The CFR was calculated as the post-dipyridamole/baseline diastolic CFV ratio. A maximal symptom-limited exercise treadmill test was performed according to a modified Bruce protocol and the exercise capacity was expressed as metabolic equivalents. The mean value for baseline diastolic CFV was 59 +/- 27 cm/s; this increased after dipyridamole to 134 +/- 57 cm/s. The CFR was 2.37 +/- 0.67. Baseline diastolic CFV correlated negatively with both exercise duration (r = -0.69; P < 0.05) and value for metabolic equivalents (r = -0.70; P < 0.05). CFR was weakly and non-significantly related to exercise duration (r = 0.40; P > 0.05) and to the value for metabolic equivalents (r = 0.32; P > 0.05). Shortening of exercise time and decreasing metabolic equivalents were correlated with increased baseline diastolic CFV. Dipyridamole-assessed CFR, was weakly related to parameters of exercise capacity.

Changes in coronary sinus pH during dipyridamole stress in patients with hypertrophic cardiomyopathy

OBJECTIVES

The presence of angina pectoris and myocardial scarring in patients with hypertrophic cardiomyopathy (HCM) suggests that myocardial ischemia is a factor in the pathophysiology of the disease. The clinical evaluation of ischaemia is problematic in HCM as baseline electrocardiographic abnormalities are frequent and thallium-201 perfusion abnormalities correlate poorly with anginal symptoms. Coronary sinus pH measurement using a catheter mounted pH electrode is a validated sensitive technique for the detection of myocardial ischaemia.

METHODS AND RESULTS

11 patients with HCM and chest pain (eight men; mean (SD) (range) age 36 (11) (19-53) years) and six controls (two men; mean (SD) (range) age 49 (11) (31-62) years) with atypical pain and normal coronary angiograms were studied. Eight patients with HCM had baseline ST segment depression of > or = 1 mm and four had reversible perfusion defects during stress 201TI scintigraphy. A catheter mounted hydrogen ion sensitive electrode was introduced into the coronary sinus and pH monitored continuously during dipyridamole infusion (0.56 mg/kg over four min). The maximal change in coronary sinus pH during dipyridamole stress was greater in patients with HCM than in controls (0.082 (0.083) (0 to -0.275) v 0.005 (0.006) (0 to -0.012), P = 0.02). In six patients (four men; mean (SD) (range) age 29 (9) (19-40 years) the development of chest pain was associated with a gradual decline in coronary sinus pH (mean 0.123 (0.089)), peaking at 442 (106) s. There were no relations among left ventricular dimensions, maximal wall thickness, and maximum pH change. In patients with HCM there was a correlation between maximum pH change and maximum heart rate during dipyridamole infusion (r = 0.70, P = 0.02).

CONCLUSION

This study provides further evidence that chest pain in patients with HCM is caused by myocardial ischaemia. The role of myocardial ischaemia in the pathophysiology of the disease remains to be determined but coronary sinus pH monitoring provides a method for quantifying and prospectively assessing its effects on clinical presentation and prognosis.

Concentration of circulating plasma endothelin in patients with angina and normal coronary angiograms

BACKGROUND

Some patients with angina pectoris and normal coronary arteriograms have reduced coronary flow reserve and abnormal endothelium dependent vasodilator responses. Endothelin-1 (ET-1), a potent vasoconstrictor, is an important modulator of microvascular function and may also have algogenic properties.

METHOD

Plasma ET-1 was measured in peripheral venous blood in 40 patients (30 women) (mean (SD) age 56 (8) years) with angina and normal coronary arteriograms and 21 normal controls (17 women) (mean (SD) age 53 (7) years). Patients with systemic hypertension, left ventricular hypertrophy, or coronary spasm were excluded. Plasma ET-1 was measured using radioimmunoassay.

RESULTS

Thirty five patients had > or = 1 mm ST segment depression during exercise. Left bundle branch block was present in four patients at rest and in one during exercise. Mean (SD) (range) concentration of ET-1 (pg/ml) was higher in patients than in controls (3.84 (1.25) (1.97-7.42) v 2.88 (0.71) (1.57-4.48) P < 0.0001). In patients with "high" (> control mean (one SD)) ET-1 concentrations (n = 23), the time to onset of chest pain during exercise was significantly shorter (6.21 (3.9) v 9.03 (3.9) min; p = 0.01) than in patients with "low" ET-1 concentrations. Of the five patients with left bundle branch block, four had plasma ET-1 concentration > 4.0 pg/ml.

CONCLUSION

Plasma endothelin is raised in patients with angina and normal coronary arteriograms and is consistent with the demonstration of endothelial dysfunction in such patients. The association between "high" plasma ET-1 and an earlier onset of chest pain during exercise suggests that endothelin may also have a role in the genesis of chest pain in patients with normal coronary arteries.

Hypertrophic cardiomyopathy. Clinical spectrum and treatment

HCM is a heterogeneous disease genotypically, phenotypically, pathophysiologically, clinically, and therapeutically. In decisions on the management of these patients, it is important to recognize this heterogeneity and to direct therapy at the predominant abnormalities.

Reversible ischaemia in hypertrophic cardiomyopathy

Atypical and typical chest pains are common symptoms in patients with hypertrophic cardiomyopathy. Some of these chest pains seem to be caused by ischaemia. It is difficult to objectively demonstrate ischaemia in hypertrophic cardiomyopathy. The first line treatment for chest pain considered to be ischaemic in patients with hypertrophic cardiomyopathy is the use of either a beta blocker or calcium blocker. Septal myectomy can be effective in patients with symptoms refractory to conventional treatment but is associated with significant morbidity and mortality. Recently dual chamber pacing has been advocated in such patients. In some cases dual chamber pacing alleviates chest pain in hypertrophic cardiomyopathy by an anti-ischaemic action, presumably by reducing the left ventricular outflow tract gradient and perhaps by causing an associated decrease in left ventricular outflow tract gradient and perhaps by causing an associated decrease in left ventricular end diastolic pressure.