Myocardial thallium 201 imaging in hypertrophic obstructive cardiomyopathy

Myocardial contrast echocardiography assessment of perfusion abnormalities in hypertrophic cardiomyopathy

Background

Perfusion defects during stress can occur in hypertrophic cardiomyopathy (HCM) from either structural or functional abnormalities of the coronary microcirculation. In this study, vasodilator stress myocardial contrast echocardiography (MCE) was used to quantify and spatially characterize hyperemic myocardial blood flow (MBF) deficits in HCM.

Methods

Regadenoson stress MCE was performed in patients with septal-variant HCM (n = 17) and healthy control subjects (n = 15). The presence and spatial distribution (transmural diffuse, patchy, subendocardial) of perfusion defects was determined by semiquantitative analysis. Kinetic analysis of time-intensity data was used to quantify MBF, microvascular flux rate (β), and microvascular blood volume. In patients undergoing septal myectomy (n = 3), MCE was repeated > 1 years after surgery. 

Results

In HCM subjects, perfusion defects during stress occurred in the septum in 80%, and in non-hypertrophied regions in 40%. The majority of septal defects (83%) were patchy or subendocardial, while 67% of non-hypertrophied defects were transmural and diffuse. On quantitative analysis, hyperemic MBF was approximately 50% lower (p < 0.001) in the hypertrophied and non-hypertrophied regions of those with HCM compared to controls, largely based on an inability to augment β, although hypertrophic regions also had blood volume deficits. There was no correlation between hyperemic MBF and either percent fibrosis on magnetic resonance imaging or outflow gradient, yet those with higher degrees of fibrosis (≥ 5%) or severe gradients all had low septal MBF during regadenoson. Substantial improvement in hyperemic MBF was observed in two of the three subjects undergoing myectomy, both of whom had severe pre-surgical outflow gradients at rest.

Conclusion

Perfusion defects on vasodilator MCE are common in HCM, particularly in those with extensive fibrosis, but have a different spatial pattern for the hypertrophied and non-hypertrophied segments, likely reflecting different contributions of functional and structural abnormalities. Improvement in hyperemic perfusion is possible in those undergoing septal myectomy to relieve obstruction. 

Trial registration

ClinicalTrials.gov NCT02560467.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12947-022-00293-2.

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.

Do myocardial perfusion SPECT and radionuclide angiography studies in adult patients with hypertrophic cardiomyopathy have prognostic implications?

BACKGROUND

Some myocardial perfusion single photon emission computed tomography (SPECT) and radionuclide ventriculography studies have suggested that the presence of regional perfusion defects and diastolic abnormalities could have prognostic implications in patients with hypertrophic cardiomyopathy (HC). The aim of this prospective study was to analyze the prognostic value of these techniques in adult patients with HC.

METHODS AND RESULTS

One hundred one patients with HC (44 women; mean age, 54 +/- 16 years; 55% obstructive) were prospectively studied by means of myocardial perfusion SPECT and radionuclide angiography. Of these patients, 55 (54.4%) had an abnormal myocardial perfusion SPECT study: 28 (27.7%) had fixed defects and 41 (40.6%) had reversible defects; 15 (14.8%) of these patients had both types of defect. Of the patients, 16% had left ventricular ejection fraction lower than 60%, 25.7% had an abnormal peak filling rate, and 51% had an abnormal time to peak filling rate. During 5.6 +/- 2.7 years of follow-up, 13 patients (12.8%) died (heart failure 8 and sudden death in 5) and 14 had one or more severe complications develop (syncope in 6, angina III-IV in 4, dyspnea III-IV in 10, and acute myocardial infarction in 3). The summed difference score was higher in patients with cardiac death (2.2 +/- 2.3 vs 1.1 +/- 1.3, P = .008), and fixed defects were more prevalent in patients with severe complications (57% vs 21%, P = .01). In the Kaplan-Meier survival plot analysis, severe complications were more likely in patients with fixed defects (P = .01) or ejection fraction lower than 60% ( P = .01).

CONCLUSIONS

Prognostic information from myocardial perfusion SPECT and radionuclide angiography has limited clinical significance with regard to cardiac death in adult patients with HC. However, the presence of fixed defects and lower ejection fraction in these patients has an adverse prognostic meaning for severe complications.

[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.

Effects of diltiazem on myocardial perfusion abnormalities during exercise in patients with hypertrophic cardiomyopathy

The effect of diltiazem on myocardial ischemia in patients with hypertrophic cardiomyopathy (HCM) was evaluated by exercise myocardial 201Tl single photon emission computed tomography (SPECT). Exercise myocardial SPECT was performed before and 8 weeks after oral administration of diltiazem (180 mg/day) in 20 patients with HCM who showed transient perfusion defects on exercise myocardial 201Tl SPECT under control conditions. SPECT images were divided into 17 segments. The 201Tl perfusion defects were visually scored and evaluated as the defect score. The transient dilation index was calculated as an index of subendocardial ischemia. Improvement of the defect score was demonstrated in 15 patients after the administration of diltiazem. The mean defect score decreased significantly from 9.90 +/- 5.17 to 5.50 +/- 4.89 (p < 0.0001). Although 16 of 20 patients showed an abnormal transient dilation index before diltiazem treatment, 16 showed improvement and 13 of these normalized after diltiazem therapy. The mean transient dilation index decreased from 1.16 +/- 0.10 to 1.02 +/- 0.09 (p < 0.0001). In conclusion, diltiazem prevents or diminishes myocardial ischemia in patients with HCM.

Transthoracic Doppler echocardiographic analysis of phasic coronary blood flow velocity in hypertrophic cardiomyopathy

OBJECTIVE

To use transthoracic Doppler echocardiography to assess coronary blood flow non-invasively in patients with hypertrophic cardiomyopathy.

DESIGN

High frequency transthoracic Doppler echocardiography was used to assess resting phasic coronary velocity patterns in patients with hypertrophic cardiomyopathy and to define the relation between coronary flow patterns and clinical, echocardiographic, and haemodynamic manifestations of this condition.

SETTING

A tertiary referral cardiothoracic centre.

METHODS

Fifteen patients (10 men and five women, mean (SD) age 49 (10.3) years) with asymmetric hypertrophic cardiomyopathy underwent high frequency (5 MHz) transthoracic Doppler echocardiographic assessment of the left anterior descending coronary artery. In addition, standard two dimensional echocardiography was performed. The results were compared with 16 normal participants (nine men and seven women, mean age 61.2 (10.7) years) who had no evidence of cardiac disease.

RESULTS

Biphasic diastolic predominant coronary artery blood velocity profiles were obtained in all patients and controls. Systolic peak blood velocity and velocity time integral were significantly reduced in the hypertrophic cardiomyopathy group compared with controls (11.3 (15.8) cm/s and 1.09 (1.78) cm v 20.5 (13.1) cm/s and 4.23 (2.80) cm, respectively, P < 0.05). A reversed pattern of systolic blood flow velocity was found in three patients with severe anterior wall and septal hypertrophy. During diastole there was prolongation of the diastolic acceleration (203 (53) ms v 110 (60) ms in controls, P < 0.05) and deceleration times (487 (200) ms v 210 (90) ms in controls, P < 0.05). There was no significant difference between those with and without symptoms or a left ventricular outflow tract gradient.

CONCLUSIONS

Patients with hypertrophic cardiomyopathy have abnormal systolic and diastolic coronary flow profiles at rest when measured by transthoracic echocardiography.

Myocardial blood flow and metabolism in patients with hypertrophic cardiomyopathy--a study with carbon-11 acetate and positron emission tomography

The underlying pathophysiology of hypertrophic cardiomyopathy (HCM) is still unclear. positron emission tomography is a suitable and promising technique for the detection of possible metabolic consequences of the disease. To assess regional myocardial blood flow and metabolism, 19 asymptomatic or only mildly symptomatic patients with HCM and 10 normal control subjects were studied using carbon-11 acetate and fluorine-18-labelled deoxyglucose (FDG) as tracers of myocardial blood flow (Ao), oxygen consumption (k), and exogenous glucose utilization. In the patients, regional Ao in the hypertrophied septum and apex (H) was similar to that in the nonhypertrophied free wall (N) (91.3 +/- 3.9% vs 92.9 +/- 3.1%; p = NS). However, the k values were significantly lower in H than in N (0.044 +/- 0.012 vs 0.060 +/- 0.016/min, p < 0.0001). The k value in N and normal control subjects (0.062 +/- 0.013) was similar. Postprandial FDG uptake was lower in H than in N (70 +/- 16 vs 91 +/- 7%; p < 0.0001) in 16 patients and slightly higher in 3 patients. Fasting FDG study showed increased FDG uptake in H in 3 out of 13 patients, suggesting a disorder of the myocardial microvascular circulation. A relative decrease in hypertrophied septal and apical oxidative metabolism and glucose utilization without any corresponding perfusion defect could reflect abnormal regional aerobic metabolism in the disproportionately thickened myocardium in patients with HCM. This suggests that a primary myocardial metabolic defect might be present in patients with HCM.

Regional myocardial blood flow and glucose utilization in symptomatic patients with hypertrophic cardiomyopathy

BACKGROUND

Previous studies suggested the presence of myocardial ischemia in symptomatic patients with hypertrophic cardiomyopathy. Positron emission tomography, a technique that can identify metabolic consequences of ischemia in coronary artery disease, permits the noninvasive measurements of regional myocardial blood flow and glucose metabolism. This new quantitative imaging approach should therefore be suitable for detecting a possible enhancement of glucose utilization in myocardium of patients with hypertrophic cardiomyopathy and thus may help to elucidate the pathomechanism of ischemia in this disease.

METHODS AND RESULTS

In 13 symptomatic patients with hypertrophic cardiomyopathy, myocardial blood flow and glucose utilization were measured with intravenous N-13-ammonia and F-18 deoxyglucose at rest and, in four patients, again during supine bicycle exercise. At rest, blood flow was significantly lower in hypertrophied than in normal myocardium (0.78 +/- 0.19 versus 0.99 +/- 0.13 mL.min-1.g-1, p < 0.025), whereas rates of glucose utilization were similar (0.88 +/- 0.31 versus 0.87 +/- 0.35 mumol.min-1.g-1). With exercise, blood flow and glucose utilization failed to increase in hypertrophic and normal segments but became more heterogeneously distributed throughout the left ventricular myocardium. Blood flow-metabolism mismatches indicative of myocardial ischemia were noted in three patients at rest and in three of the four patients during exercise and were due to reduced flow in the presence of maintained glucose uptake. The discordance between flow and glucose metabolism in hypertrophied myocardium was significantly more prominent in younger than in older patients.

CONCLUSIONS

Normal or even elevated rates of glucose utilization and the presence of diminished blood flow in hypertrophied relative to normal myocardium suggest the presence of myocardial ischemia in symptomatic hypertrophic cardiomyopathy. The age dependence of blood flow metabolism disparity suggests differences in the underlying pathophysiology or severity of disease.

Myocardial metabolic, hemodynamic, and electrocardiographic significance of reversible thallium-201 abnormalities in hypertrophic cardiomyopathy

BACKGROUND

Exercise-induced abnormalities during thallium-201 scintigraphy that normalize at rest frequently occur in patients with hypertrophic cardiomyopathy. However, it is not known whether these abnormalities are indicative of myocardial ischemia.

METHODS AND RESULTS

Fifty patients with hypertrophic cardiomyopathy underwent exercise 201Tl scintigraphy and, during the same week, measurement of myocardial lactate metabolism and hemodynamics during pacing stress. Thirty-seven patients (74%) had one or more 201Tl abnormalities that completely normalized after 3 hours of rest; 26 had regional myocardial 201Tl defects, and 26 had apparent left ventricular cavity dilatation with exercise, with 15 having coexistence of these abnormal findings. Of the 37 patients with reversible 201Tl abnormalities, 27 (73%) had metabolic evidence of myocardial ischemia during rapid atrial pacing (myocardial lactate extraction of 0 mmol/l or less) compared with four of 13 patients (31%) with normal 201Tl scans (p less than 0.01). Eleven patients had apparent cavity dilatation as their only 201Tl abnormality; their mean postpacing left ventricular end-diastolic pressure was significantly higher than that of the 13 patients with normal 201Tl studies (33 +/- 5 versus 21 +/- 10 mm Hg, p less than 0.001). There was no correlation between the angiographic presence of systolic septal or epicardial coronary arterial compression and the presence or distribution of 201Tl abnormalities. Patients with ischemic ST segment responses to exercise had an 80% prevalence rate of reversible 201Tl abnormalities and a 70% prevalence rate of pacing-induced ischemia. However, 69% of patients with nonischemic ST segment responses had reversible 201Tl abnormalities, and 55% had pacing-induced ischemia.

CONCLUSIONS

Reversible 201Tl abnormalities during exercise stress are markers of myocardial ischemia in hypertrophic cardiomyopathy and most likely identify relatively underperfused myocardium. In contrast, ST segment changes with exercise and systolic compression of coronary arteries on angiography are unreliable markers of inducible myocardial ischemia in hypertrophic cardiomyopathy. Apparent cavity dilatation during 201Tl scintigraphy may indicate ischemia-related changes in left ventricular filling, with elevation in diastolic pressures and endocardial compression.

Hypertrophic cardiomyopathy: prognosis with medical or surgical therapy

Over the past 30 years, knowledge of the natural history and effects of therapy in patients with hypertrophic cardiomyopathy has expanded greatly, but progress has been hampered by its variable patterns of expression. Many but not all patients show symptomatic improvement with medical treatment. Chronic beta blockage does not appear to affect long-term survival, whereas results with calcium channel blockade by verapamil have been encouraging; however, they await confirmation, and verapamil may be hazardous in some patients with severe left ventricular (LV) outflow tract obstruction and elevated LV end-diastolic pressure. Reported beneficial effects of amiodarone on survival also require further study. Surgical therapy has become the treatment of choice for medically refractory patients with proven outflow tract obstruction. In several centers, the operative risk is low, and long-term follow-up demonstrates prolonged symptomatic relief. It is hoped that work currently underway will provide more definitive information on the long-term effects of the role of calcium channel blockers, antiarrhythmic medications, and the long-term effects of surgical therapy on survival of patients with this disorder.

Comparison of proximal left anterior descending and circumflex coronary artery dimensions in aortic valve stenosis and hypertrophic cardiomyopathy

To examine the "adequacy" of basal coronary flow in ventricular hypertrophy, the relation between proximal coronary artery dimensions and regional ventricular mass in aortic valve stenosis (AS) and hypertrophic cardiomyopathy (HC) was evaluated. Coronary artery size was determined by quantitative coronary arteriography while global/regional ventricular mass was calculated using computer-processed biplane 2-dimensional echocardiography. In comparison to 18 "normal" subjects, left anterior descending coronary dimensions were significantly larger in those with hypertrophy (normal 3.32 +/- 0.54, AS 3.82 +/- 0.71, HC 4.72 +/- 0.81 mm, p less than 0.05), with progressive increases in left anterior descending/circumflex coronary diameter ratios (normal 1.04 +/- 0.14, AS 1.18 +/- 0.19, HC 1.25 +/- 0.31, p less than 0.01). Compared to the AS group, indexed anteroseptal mass was greater in the HC subjects (AS 40.9 +/- 8.9 vs HC 72.1 +/- 21 g/m2, p less than 0.001). Both septal width/left anterior descending coronary diameter ratios (AS 3.61 +/- 1.06 vs HC 4.85 +/- 1.17 mm/mm, p less than 0.05) and indexed anteroseptal mass/left anterior descending coronary diameter ratios (AS 11.2 +/- 3.0 vs HC 15.6 +/- 3.4 g/m2/mm, p less than 0.01) were greater in HC subjects. Increased coronary dimensions were observed in both AS and HC, with the greatest changes noted within the left anterior descending distribution in HC, but when analyzed with respect to regional ventricular mass, these subjects demonstrated relative "inadequate" enlargement in coronary artery diameters. Underdeveloped epicardial coronary arteries may contribute to anteroseptal myocardial ischemia, with resultant angina pectoris, increased ventricular ectopic activity and sudden death in HC.

Verapamil prevents silent myocardial perfusion abnormalities during exercise in asymptomatic patients with hypertrophic cardiomyopathy

Recent studies indicate that reversible 201Tl perfusion defects, compatible with silent myocardial ischemia, commonly develop during exercise in asymptomatic or mildly symptomatic patients with hypertrophic cardiomyopathy (HCM). To determine whether this represents a dynamic process that may be modified favorably by medical therapy, we studied 29 asymptomatic or minimally symptomatic patients with HCM, aged 12-55 years (mean, 28), with exercise 201Tl emission computed tomography under control conditions and again after 1 week of oral verapamil (mean dosage, 453 mg/day). Treadmill time increased slightly during verapamil (21.0 +/- 3.6 to 21.9 +/- 2.7 minutes, p less than 0.005), but peak heart rate-blood pressure product was unchanged (26.3 +/- 6.0 X 10(3) compared with 25.0 +/- 6.4 X 10(3). Two midventricular short-axis images per study were divided into five regions each, and each of these 10 regions was then analyzed on a 0-2 scale by three observers blinded with regard to the patients' therapy. Average regional scores of 1.5 or less were considered to represent perfusion defects, and a change in regional score of 0.5 or more was considered to constitute a significant change. During control studies, 15 patients (52%) developed perfusion defects with exercise (average, 3.7 regions per patient). In 14 of these patients, all perfusion defects completely reversed after 3 hours of rest; one patient had fixed defects. After administration of verapamil, exercise perfusion scores improved in 10 of the 14 patients (71%) with reversible defects; there was overall improvement in 34 of 50 (68%) regions with initially reversible perfusion defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional myocardial blood flow and metabolism at rest in mildly symptomatic patients with hypertrophic cardiomyopathy

Previous observations and clinical manifestations suggest the presence of ischemia in the disproportionately thickened septum of patients with hypertrophic cardiomyopathy. Metabolic consequences of ischemia can be demonstrated with positron emission tomography. Therefore, 10 patients with hypertrophic cardiomyopathy and an echocardiographic septum to posterior wall thickness ratio of 1.8 +/- 0.4 cm (range 1.3 to 2.5) were studied with the use of nitrogen (N)-13 ammonia, carbon (C)-11 palmitate and fluoro (F)-18 2-deoxyglucose as tracers of myocardial blood flow, fatty acid metabolism and exogenous glucose utilization. The results of positron emission tomography in 9 patients with hypertrophic cardiomyopathy were compared with those in 10 normal volunteers. In the hypertrophic cardiomyopathy group, observed myocardial activity of N-13 ammonia and C-11 palmitate in the septum was similar to that in the lateral wall. Septum to lateral wall tissue activity ratios averaged 1.04 +/- 0.15 for N-13 ammonia and 1.04 +/- 0.18 for C-11 palmitate, and were similar to those in the normal volunteers (0.98 +/- 0.07 and 0.98 +/- 0.03, respectively; p = NS). Myocardial clearance half-time and residual fraction of C-11 palmitate did not differ significantly between the septum and lateral wall. However, F-18 2-deoxyglucose uptake was significantly lower in the septum than in the lateral wall (15,768 +/- 4,314 versus 19,818 +/- 5,234 counts/pixel; p less than 0.003). The mean septum to lateral wall activity ratio of 0.83 +/- 0.21 was less than that observed in normal volunteers (0.92 +/- 0.07; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired myocardial perfusion in patients with hypertrophic cardiomyopathy: assessment with digital subtraction coronary arteriography

To study the clinical significance of abnormal myocardial perfusion in patients with hypertrophic cardiomyopathy (HCM), we performed a computerized washout analysis of digital subtraction coronary arteriograms in 28 patients with HCM and 16 control subjects. The contrast disappearance half-life (T1/2) was calculated from a time-density curve generated in the four sectors of the myocardium perfused by the left anterior descending coronary artery and the mean T1/2 was calculated by averaging T1/2 values for these four sectors. Patients with HCM demonstrated longer T1/2 in the ventricular septal region than control subjects. Thirteen (46%) of the patients with HCM presented abnormally longer mean T1/2 values, suggesting impaired myocardial perfusion. Family histories of HCM were more frequent in patients with abnormal mean T1/2 values (92% vs 47%; p less than 0.05). On the exercise stress test, patients with abnormal T1/2 values presented significantly lower exercise tolerance with more frequent exercise-induced ST segment depression (62% vs 13%; p less than 0.05). However, there were no significant differences between the two groups with regard to ventricular wall thickness, left ventricular end-diastolic pressure, or the severity of systolic narrowing of the coronary arteries. These findings suggest that 13 (46%) of the patients with HCM have impaired myocardial perfusion, which may be a manifestation of intramural coronary artery disease in addition to left ventricular hypertrophy, elevated left ventricular end-diastolic pressure, or systolic narrowing of the coronary arteries. Additionally, significant association of the prolonged T1/2 with a familial occurrence of HCM and depressed exercise tolerance with ST segment depression imply that impaired myocardial perfusion could be an important inherent pathophysiological state leading to myocardial ischemia during exercise.

Myocardial perfusion abnormalities in patients with hypertrophic cardiomyopathy: assessment with thallium-201 emission computed tomography

Myocardial ischemia may play a critical role in the symptomatic presentation and natural history of hypertrophic cardiomyopathy (HCM). To assess the relative prevalence and functional significance of myocardial perfusion abnormalities in patients comprising the broad clinical spectrum of HCM, we studied 72 patients (ages 12 to 69 years, mean 40) using thallium-201 emission computed tomography. Imaging was performed immediately after maximal exercise and again after a 3 hr delay. Regional perfusion defects were identified in 41 of the 72 patients (57%). Fixed or only partially reversible defects were evident in 17 patients, 14 of whom (82%) had left ventricular ejection fractions of less than 50% at rest. Twenty-four patients demonstrated perfusion defects during exercise that completely reversed at rest; all had normal or hyperdynamic left ventricular systolic function (ejection fraction greater than or equal to 50%). Perfusion abnormalities were present in all regions of the left ventricle. However, the fixed defects were observed predominantly in segments of the left ventricular wall that were of normal or only mildly increased (15 to 20 mm) thickness; in contrast, a substantial proportion (41%) of the completely reversible defects occurred in areas of moderate-to-marked wall thickness (greater than or equal to 20 mm, p less than .001). Neither a history of chest pain nor its provocation with treadmill exercise was predictive of an abnormal thallium study, since regional perfusion defects were present in 10 of 18 (56%) completely asymptomatic patients, compared with 31 of 54 (58%) symptomatic patients. These data indicate that myocardial perfusion abnormalities occur commonly among patients with HCM. Fixed or only partially reversible defects suggestive of myocardial scar and/or severe ischemia occur primarily in patients with impaired systolic performance. Completely reversible perfusion abnormalities occur predominantly in patients with normal or supranormal left ventricular systolic function. Such dynamic changes in regional thallium activity may reflect an ischemic process that contributes importantly to the clinical manifestations and natural history of HCM.

Quantitative analysis of narrowings of intramyocardial small arteries in normal hearts, hypertensive hearts, and hearts with hypertrophic cardiomyopathy

To clarify the pathophysiologic role of intramyocardial small artery (IMSA) diseases in hypertrophied hearts, narrowings of the IMSA were quantitatively evaluated in 39 autopsied hearts, 10 from patients with typical hypertrophic cardiomyopathy (HCM), four from patients with HCM showing features mimicking dilated cardiomyopathy (DCM-like HCM), 10 from patients with hypertension, and 15 from normal adults. The relations of narrowings of the IMSA to myocytic hypertrophy, myocardial fiber disarray, and fibrosis were also examined. The external caliber and the ratio of the luminal area to the total vascular area (percent luminal area, % lumen) were calculated by an image analyzer in 85 to 203 IMSAs from each patient. The external calibers of the IMSAs were similar among groups of hearts with HCM, hypertensive hearts, and normal hearts but were greater in those with DCM-like HCM. The mean % lumen of the IMSAs was similarly reduced in the hearts with HCM (29 +/- 5% in the ventricular septum and 31 +/- 5% in the left ventricular free wall) and in hypertensive hearts (30 +/- 8% and 31 +/- 7%) compared with that in normal hearts (40 +/- 5% and 38 +/- 5%) and was the lowest in the ventricular septum of hearts with DCM-like HCM (17 +/- 3%). The mean % lumen of the IMSA was inversely correlated with heart weight (r = -.59), the mean size of myocytes (r = -.66 in the ventricular septum, r = -.63 in the free wall), and percent fibrotic area in the septum (r = -.68). The mean % lumen values of the IMSAs in the tissues with and without disarray in the hearts with HCM were similar. Thus IMSA disease is of pathophysiologic importance in patients with HCM, DCM-like HCM in particular, or with hypertension.

Severe functional limitation in patients with hypertrophic cardiomyopathy and only mild localized left ventricular hypertrophy

Ten patients with nonobstructive hypertrophic cardiomyopathy and only mild localized left ventricular hypertrophy who had severe symptoms of cardiac failure are described. During a mean follow-up period of 7 years, 6 of these 10 patients showed a substantial increase in left ventricular internal dimension (6 to 15 mm, mean 10) as assessed with M-mode echocardiography, although absolute left ventricular cavity size remained within normal limits in 5 of the 6. Four patients demonstrated substantial septal thinning (5 to 14 mm, mean 8). Left ventricular diastolic function, assessed by radionuclide angiography in nine patients, was impaired in eight who showed decreased peak filling rate (less than 2.5 end-diastolic volumes/s) and prolonged time to peak rate of filling (greater than or equal to 180 ms). Furthermore, left ventricular systolic function, usually supernormal in patients with hypertrophic cardiomyopathy, was depressed (ejection fraction less than or equal to 45%) in six patients. Hence, a subset of patients was identified with nonobstructive hypertrophic cardiomyopathy and only mild localized left ventricular hypertrophy who experienced severe cardiac symptoms. The majority of these patients showed both systolic and diastolic left ventricular dysfunction in the presence of a progressive increase in left ventricular internal dimension (but without absolute left ventricular dilation) or ventricular septal thinning or both. Such patients may represent an important component of the natural history of hypertrophic cardiomyopathy which has not been previously fully appreciated.

Clinical studies on diabetic myocardial disease using exercise testing with myocardial scintigraphy and endomyocardial biopsy

Nine diabetics without significant coronary stenosis participated in an exercise testing protocol with thallium-201 myocardial scintigraphy. Endomyocardial biopsy of right ventricle was also obtained. There were 4 patients with abnormal perfusion (positive group) and 5 patients with normal perfusion (negative group). All cases of the positive group were familial diabetics and there was only one case of dietary treatment, whereas in the negative group, there were only 2 cases of familial diabetics and 3 cases receiving dietary treatment. No statistical differences between the positive and negative groups were observed for the data of exercise performance and hemodynamic parameters in cardiac catheterization at rest. However, the mean ejection fraction in the positive group (62 +/- 13%) was significantly lower than in the negative group (77 +/- 4%). In both groups, the mean diameter of myocardial cells and the mean percent fibrosis of biopsy specimens showed significant increases compared with the control group. The mean percent fibrosis in the positive group (24.1 +/- 8.5%) compared with that in the negative group (16.5 +/- 5.9%) showed a tendency to increase. It is suggested that the abnormal perfusion of thallium-201 in the positive group indicates subclinically a pathological change of microcirculation caused by diabetes mellitus.

Myocardial ischemia in patients with hypertrophic cardiomyopathy: contribution of inadequate vasodilator reserve and elevated left ventricular filling pressures

To study the mechanism and hemodynamic significance of myocardial ischemia in hypertrophic cardiomyopathy, 20 patients (nine with resting left ventricular outflow tract obstruction greater than or equal to 30 mm Hg) with a history of angina pectoris and angiographically normal coronary arteries underwent a pacing study with measurement of great cardiac vein flow, lactate and oxygen content, and left ventricular filling pressure. Compared with 28 control subjects without hypertrophic cardiomyopathy, their resting coronary blood flow was higher (91 +/- 27 vs 66 +/- 17 ml/min; p less than .001) and their coronary resistance was lower (1.13 +/- 0.38 vs 1.55 +/- 0.45 mm Hg/ml/min; p less than .001). Left ventricular end-diastolic pressure (16 +/- 6 vs 11 +/- 3 mm Hg; p less than .001) and pulmonary arterial wedge pressure (13 +/- 5 vs 7 +/- 3 mm Hg; p less than .001) were significantly higher in patients with hypertrophic cardiomyopathy. During pacing, coronary flow rose in both groups, although coronary and myocardial hemodynamics differed greatly. In contrast to the linear increase in flow in control subjects up to heart rate of 150 beats/min (66 +/- 17 to 125 +/- 28 ml/min), patients with hypertrophic cardiomyopathy demonstrated an initial rise in flow to 133 +/- 31 ml/min at an intermediate heart rate of 130 beats/min. At this point, 12 of 20 patients developed their typical chest pain. With continued pacing to a heart rate of 150 beats/min, mean coronary flow fell to 114 +/- 29 ml/min (p less than .002), with 18 of 20 patients experiencing their typical chest pain and metabolic evidence of myocardial ischemia. This fall in coronary flow was associated with a substantial rise in left ventricular end-diastolic pressure (30 +/- 9 mm Hg immediately after peak pacing). In the 14 patients whose coronary flow actually fell from intermediate to peak pacing, the rise in left ventricular end-diastolic pressure in the same interval was greater than that of the six patients whose flow remained unchanged or increased (11 +/- 8 vs 2 +/- 2 mm Hg; p less than .01). In addition, despite metabolic and hemodynamic evidence of myocardial ischemia, the arteriovenous O2 difference actually narrowed at peak pacing. Thus most patients with hypertrophic cardiomyopathy achieved maximum coronary vasodilation and flow at modest increases in heart rate. Elevation in left ventricular filling pressure, probably related to ischemia-induced changes in ventricular compliance, was associated with a decline in coronary flow.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of verapamil therapy on left ventricular performance at rest and during exercise in hypertrophic cardiomyopathy

To determine the hemodynamic effect of verapamil at rest and during exercise, 18 patients with hypertrophic cardiomyopathy were studied before and after 7 weeks of treatment with oral verapamil (maximal dose, 720 mg/day). At rest and at peak exercise, verapamil produced a significant increase in left ventricular (LV) systolic performance in terms of stroke volume index (rest, from 43 +/- 11 to 53 +/- 11 ml/m2, p less than 0.001; exercise, from 46 +/- 11 to 51 +/- 10 ml/m2, p less than 0.01), whereas heart rate decreased (rest, from 81 +/- 14 to 70 +/- 11 min-1, p less than 0.001; exercise, from 150 +/- 21 to 141 +/- 18 min-1, p less than 0.01). Cardiac index at rest and during exercise remained unchanged. Systolic vascular resistance did not change at rest, but decreased significantly during exercise (974 +/- 243 to 874 +/- 174 dynes s cm-5; p less than 0.05). After verapamil administration, pulmonary artery pressures did not change at rest, but decreased significantly during exercise. This was probably due to a shift in the LV pressure-volume relation. The improvement in LV hemodynamics was associated with a significant increase in exercise capacity. The findings of this study indicate that in patients with hypertrophic cardiomyopathy, hemodynamic improvement at rest and during exercise can be achieved by chronic administration of verapamil.