Immunohistochemical localization of basic and acidic fibroblast growth factors in the developing rat heart

BACKGROUND

We used biochemical and immunohistochemical techniques to investigate the expression and distribution of immunoreactive basic and acidic fibroblast growth factors (bFGF and aFGF, respectively) in the hearts of rat embryos (11-20 days of gestation) and of postnatal rats (1-35 days after birth). Our purpose was to assess the relation between the cellular distribution of these growth factors and histogenetic and morphogenetic events in the developing heart.

METHODS AND RESULTS

Western-blot analysis of heparin-bound material from neonatal heart extracts identified a single band with a molecular weight of approximately 18 kD for both bFGF and aFGF. Five antibodies for bFGF and three for aFGF showed superimposable distribution of immunoreactive bFGF and aFGF in the heart at each stage examined. At the cellular level, these peptides were localized in the cytoplasm and extracellular matrix. In the myocytes, immunostaining was positive throughout the embryonic and neonatal periods. In the majority of the mesenchymal cells of the cushions and endothelial cells of endocardium and vessels, staining was also positive. In the smooth muscle cells of the aorta, other large arteries, and coronary arteries, immunostaining was intensely positive at early stages of development but became faint or negative with increasing cell differentiation.

CONCLUSIONS

The wide distribution of immunoreactive bFGF and aFGF that we identified in the developing rat heart suggests that these growth factors play an important role in heart cytodifferentiation and morphogenesis. Their superimposable distribution may reflect functional interaction. The progressive changes in their distribution suggest a changing role for these peptides during organogenesis.

Comparison of exercise testing with studies of coronary flow reserve in patients with microvascular angina

Abnormal small coronary artery function may cause limited coronary flow responses to stress, resulting in anginal symptoms and ischemia in some patients with chest pain despite angiographically normal coronary arteries. To assess the exercise hemodynamic correlates of coronary flow abnormalities measured in the cardiac catheterization laboratory, 105 patients with microvascular angina (defined as an increase in coronary vascular resistance during pacing stress after ergonovine administration in the absence of significant epicardial constriction and associated with provocation of the patient's typical chest pain) and 27 patients without any coronary flow abnormality (normal) were analyzed. Of the 105 patients with microvascular angina, 75 had normal electrocardiographic responses to treadmill exercise testing, 22 had ischemic responses, and eight had bundle branch block during exercise. All 27 normal patients had normal electrocardiographic responses to exercise. Patients with ischemic electrocardiographic responses (0 +/- 7%, p less than 0.01), and those with bundle branch block (-2 +/- 6%, p less than 0.01) had abnormal left ventricular ejection fraction responses to exercise compared with the normal group, who demonstrated an 8 +/- 6% increase in left ventricular ejection fraction by radionuclide angiography during exercise, and microvascular angina patients with a normal electrocardiographic response to exercise, who demonstrated a 5 +/- 7% increase in ejection fraction. Although the microvascular response to ergonovine was no different among the three microvascular angina exercise groups, the administration of dipyridamole caused less coronary vasodilation in those patients with apparently ischemic or bundle branch block responses to exercise compared with those with normal electrocardiograms during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Heparin promotes the formation of extracardiac to coronary anastomoses in a canine model

We developed a canine model for the in vivo utilization of angiogenesis factors to promote revascularization of a collateral-dependent area of the heart and assessed the potential of heparin in this preparation. Ameroids were placed on the proximal left anterior descending coronary artery (LAD) of 29 dogs, and the left internal mammary artery (IMA) was implanted in an intramyocardial tunnel in proximity to the LAD. A tube positioned in the distal IMA provided a continuous retrograde infusion directly into the vessel from an implanted pump. Heparin (15 or 150 U/h) or saline vehicle was infused. After 8 wk, regional myocardial blood flow was assessed in the anesthetized state during adenosine-induced vasodilatation, before and during occlusion of the IMA. The IMA provided a greater proportion of maximal collateral flow in heparin-treated dogs (22 +/- 5%, n = 17) than in saline-treated dogs (9 +/- 2%, n = 12, P less than 0.05). Thus continuous infusion of heparin promotes the formation of collaterals between the extracardiac artery and the myocardial circulation, establishing the feasibility of targeting angiogenic agents for myocardial revascularization.

Exercise testing in patients with microvascular angina

The widespread use of exercise testing for the detection of myocardial ischemia in patients suspected of having coronary artery disease led to the detection of ischemic changes in many subjects who subsequently were found to have angiographically normal epicardial vessels--the false positive response. Such a result is usually interpreted as indicating that the subject's chest pain is of noncardiac origin. For the past several years, we have studied the mechanism of pain resembling angina that occurs in patients with normal epicardial coronary arteries demonstrated by angiography; we believe these studies have shed some light on this problem. Patients with angiographically normal coronary arteries who present because of a history of angina-like pain and/or ischemic changes detected during exercise electrocardiogram testing were evaluated by measuring great cardiac vein flow (under baseline conditions and after cardiac pacing, with and without intravenous administration of ergonovine) and by radionuclide angiography before and during exercise. We found that a substantial number of these subjects showed inadequate coronary vasodilator reserve and had exercise-induced left ventricular dysfunction suggestive of myocardial ischemia. We concluded from our results that there is a distinct clinical syndrome of myocardial ischemia caused by abnormal resistance responses of the prearteriolar coronary microvasculature. We now refer to this syndrome as microvascular angina. In a series of 115 patients with documented microvascular angina, we also found that only 10% had ischemic ST changes with exercise testing (2% of the men and 17% of the women developed ischemic ST segment changes).(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction of the frequency and duration of ambulatory myocardial ischemia in patients with stable coronary artery disease by determination of the ischemic threshold from exercise testing: importance of the exercise protocol

The relation between ambulatory myocardial ischemia and the results of exercise testing in patients with ischemic heart disease remains undefined, because of the dissimilar results of previous reports. To further investigate this issue and, in particular, to ascertain the importance of the exercise protocol in determining that relation, 70 patients with stable coronary artery disease underwent 48 h ambulatory electrocardiographic (ECG) monitoring and treadmill exercise tests after withdrawal of medications. Patients exercised using two different protocols with slow (National Institutes of Health [NIH] combined protocol) and brisk (Bruce protocol) work load increments. Exercise duration was longer with the NIH combined protocol (14.1 +/- 5 versus 6.8 +/- 2 min; p less than 0.0001), but the maximal work load and peak heart rate achieved were greater with the Bruce protocol (9.8 +/- 2 versus 6.5 +/- 2 METs, and 142 +/- 19 versus 133 +/- 22 beats/min, respectively; p less than 0.0001). A close inverse correlation between exercise testing and the results of ambulatory ECG monitoring was observed using the NIH combined protocol; the strongest correlation was observed between time of exercise at 1 mm of ST segment depression and number of ischemic episodes (r = -0.86; p less than 0.0001). With the Bruce protocol a significantly weaker inverse correlation was found (r = -0.35). The mean heart rate at the onset of ST segment depression was similar during monitoring and during exercise testing with the NIH combined protocol (97.2 +/- 13 versus 101.0 +/- 17 beats/min, respectively) but it was significantly higher (110.4 +/- 13) when using the Bruce protocol (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Value of electrophysiologic studies in hypertrophic cardiomyopathy treated with amiodarone

The relation of electrophysiologic effects of amiodarone to long-term outcome was studied in 35 patients with hypertrophic cardiomyopathy (HC). Indications for electrophysiologic studies were: cardiac arrest (n = 3), syncope/presyncope (n = 27) and asymptomatic ventricular tachycardia (VT) (n = 5). Twenty-eight patients (80%) had VT, 3 (9%) atrial tachycardia and 3 (9%) paroxysmal atrial fibrillation during 24-hour Holter monitoring. The studies were repeated after a total amiodarone dose of 58 +/- 122 g and during a maintenance median daily dose of 400 mg. Amiodarone abolished paroxysmal atrial arrhythmias in all 6 patients. However, it caused marked atrioventricular nodal conduction abnormality in 3 patients and heart block or marked HV interval prolongation (to greater than or equal to 100 ms) in 4 patients. Sustained VT was induced in 26 patients (74%) at baseline study and in 23 patients (66%) taking amiodarone therapy. With amiodarone, VT was no longer inducible or was more difficult to induce in 11 patients (31%), and the drug abolished VT during Holter monitoring in all patients. However, VT was easier to induce with amiodarone or was induced only with amiodarone in 18 (51%) patients. Amiodarone significantly slowed the rate of induced VT (from 248 +/- 29 to 214 +/- 37 beats/min, p less than 0.001). This was associated with a change in its morphology from polymorphic to monomorphic VT in 7 patients. During a follow up of 18 +/- 14 months (range 2 to 56), amiodarone was discontinued because of adverse effects in 8 patients (23%).(ABSTRACT TRUNCATED AT 250 WORDS)

Sudden death during empiric amiodarone therapy in symptomatic hypertrophic cardiomyopathy

Amiodarone is reported to improve symptoms and to prevent sudden death in patients with hypertrophic cardiomyopathy (HC). Amiodarone treatment (loading dose 30 g given over 6 weeks; maintenance dose 400 mg/day) was prospectively evaluated in 50 patients with HC in whom the drug was initiated because of symptoms refractory to conventional drug therapy (calcium antagonists and beta blockers). Twenty-one (42%) patients had ventricular tachycardia (VT) during Holter monitoring. Amiodarone significantly and often markedly improved the patients' New York Heart Association functional class status (from 3.3 to 2.7 at 2 months, p less than 0.001) and treadmill exercise duration (p less than 0.001). Eight patients, however, died (7 suddenly) during a mean follow-up period of 2.2 +/- 1.8 years. Of the 7 sudden deaths, 6 occurred within 5 months of initiation of treatment. The 6-month and 1- and 2-year survival rates were 87, 85 and 80%, respectively. The survival rate of patients with VT was significantly worse than that of patients without VT (61 vs 97% at 2 years; p less than 0.01). Sudden death occurred despite abolition of VT on Holter monitoring. Amiodarone increased left ventricular peak filling rate by radionuclide angiography in 20 of 33 patients (61%) (p less than 0.01). Decrease in peak left ventricular filling rate within 10 days of amiodarone therapy (8 of 33 patients) was associated with subsequent sudden death (p less than 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Airway hyperresponsiveness in patients with microvascular angina. Evidence for a diffuse disorder of smooth muscle responsiveness

Anginal chest pain in patients with angiographically normal coronary arteries may be caused by a limited coronary flow response to stress because of abnormal function of the coronary microcirculation (microvascular angina). Studies of forearm arterial function suggested that patients with microvascular angina may have a diffuse disorder of smooth muscle tone. Because dyspnea is common in these patients and seems disproportionate to the severity of myocardial ischemia, we studied air flow (forced expiratory volume in 1 second, or FEV1) in the basal state and after methacholine inhalation to determine whether bronchial smooth muscle is affected in this syndrome. Five of 36 patients with microvascular angina had a basal FEV1 of less than 70% of that predicted and did not receive methacholine. Of the remaining 31 patients, 14 (45%) had a more-than-20% reduction in FEV1 after methacholine inhalation (as much as 25 mg/ml), a response significantly greater than that of nine patients with heart disease (0%, p less than 0.025) and 24 normal volunteers of similar age and gender distribution (13%, p less than 0.025). Furthermore, the product of the methacholine dose inhaled and the magnitude of decline in FEV1 from baseline (methacholine response score) was significantly lower in patients with microvascular angina than in normal volunteers (16 +/- 8.6 versus 22.2 +/- 3.7, p = 0.026). We conclude that airway hyperresponsiveness is frequently demonstrable in patients with microvascular angina; these findings are consistent with our hypothesis that this syndrome may represent a more generalized abnormality of vascular and nonvascular smooth muscle function.

Abnormal cardiac sensitivity in patients with chest pain and normal coronary arteries

The causes of chest pain in patients found to have angiographically normal coronary arteries during cardiac catheterization remain controversial. Cardiac sensitivity to catheter manipulation, pacing at various stimulus intensities and intracoronary injection of contrast medium was examined in several groups of patients who underwent cardiac catheterization. Right heart (especially right ventricular) catheter manipulation and pacing and intracoronary contrast medium provoked chest pain typical of that previously experienced in 29 (81%) of 36 patients with chest pain and angiographically normal coronary arteries and 15 (46%) of 33 symptomatic patients with hypertrophic cardiomyopathy. In contrast, only 2 (6%) of 33 symptomatic patients with coronary artery disease experienced their typical chest pain with these sensitivity tests (p less than 0.001). None of 10 patients with valvular heart disease but without a chest pain syndrome experienced any sensation with these tests. Cutaneous pain threshold testing demonstrated that patients with chest pain and normal coronary arteries had a higher pain threshold to thermal stimulation compared with patients who had coronary artery disease or hypertrophic cardiomyopathy. No relation existed between cardiac sensitivity and cutaneous sensitivity testing. Thus, patients who have chest pain despite angiographically normal coronary arteries may have abnormal cardiac sensitivity to a variety of stimuli. This increased sensitivity may be of causal importance to their chest pain syndrome or may contribute to their perception of ischemia-induced pain. The same phenomenon was also commonly seen in symptomatic patients with hypertrophic cardiomyopathy. Whether this phenomenon represents abnormal activation of pain receptors within the heart or abnormal processing of visceral afferent neural impulses in the peripheral or central nervous system is unknown.

Creation of anastomoses between an extracardiac artery and the coronary circulation. Proof that myocardial angiogenesis occurs and can provide nutritional blood flow to the myocardium

The purpose of this investigation was to determine whether blood vessels could develop de novo between an extracardiac artery and a collateral-dependent zone of the heart and to quantify the nutritive blood flow afforded by the new vessels. We also adapted the preparation so that angiogenically active agents could be chronically administered directly to the site of neovascularization in subsequent studies. To induce neovascularization between a systemic artery and the coronary circulation, the left internal mammary artery (IMA) was implanted in an intramyocardial tunnel in proximity to the left anterior descending coronary artery (LAD). A tube situated in the distal IMA connected to an implanted pump provided for continuous intra-arterial infusion at the site of angiogenesis. During the same procedure, an ameroid constrictor was placed on the proximal LAD, rendering its perfusion territory collateral dependent during a 2-3 week period. After 8 weeks, the functional capacity of the anastomoses established between the implanted IMA and the LAD territory was assessed by determining regional myocardial blood flow under basal conditions, during adenosine-induced vasodilatation, and during differential occlusions of the IMA and left circumflex coronary artery (LCCA). For all dogs, IMA occlusion decreased maximal LAD territory flow from 1.31 +/- 0.11 to 1.16 +/- 0.10 ml/min/g (p less than 0.005). Occlusion of the LCCA decreased LAD zone flow to 0.73 +/- 0.12 ml/min/g, whereas occlusion of the IMA in addition to the LCCA further decreased LAD zone flow to 0.42 +/- 0.11 ml/min/g (p less than 0.02). The IMA provided measurable nutritive blood flow in seven of 12 dogs, and in these dogs, the artery provided 30.0 +/- 2.5% of total LAD zone collateral conductance under conditions of maximal vasodilatation (range, 23-42%). We conclude that angiogenesis can occur between an implanted internal mammary artery and the native coronary circulation in dogs, providing modest nutritive blood flow to a collateral-dependent region. Further studies will be necessary to determine whether direct, local infusion of angiogenically active factors can enhance neovascularization and whether sufficient flow can be reliably supplied to make some variant of this approach clinically applicable.

Influence of extracellular magnesium on capillary endothelial cell proliferation and migration

We investigated the role of extracellular magnesium on capillary endothelial cell migration and proliferation, components of endothelial cell function that play an important role in angiogenesis and wound healing. Cell migration and proliferation were tested in six different MgSO4 concentrations and in various culture conditions. The Boyden chamber procedure was used to evaluate migration of bovine adrenal cortex capillary endothelial cells. We found that low magnesium concentration inhibited cell migration, but a dose-dependent increase in migration was observed when magnesium level was increased beyond the normal serum concentration (up to 2.4 mM magnesium; p less than 0.0001). Cell proliferation was also inhibited by very low magnesium concentration, an effect observed under all conditions studied. When cell proliferation was stimulated by acidic or basic fibroblast growth factors, it appeared that a ceiling was reached, an increasing magnesium concentration had no additional stimulatory effect. However, a dose-dependent increase in proliferation (p less than 0.005) was observed when magnesium concentration was increased above the normal serum level (0.8 mM) in culture conditions that did not cause marked cell proliferation. Thus, magnesium has an important role in endothelial cell migration and proliferation: very low extracellular magnesium concentrations inhibit and supranormal levels enhance both migration and proliferation. These results suggest that magnesium deficiency might adversely influence the healing and reendothelialization of vascular injuries and the healing of myocardial infarction and might also result in delayed or inadequate angiogenesis, effects potentially leading to infarct expansion and inadequate collateral development.

Abnormal endothelium-dependent vascular relaxation in patients with essential hypertension

BACKGROUND

Endothelium regulates vascular tone by influencing the contractile activity of vascular smooth muscle. This regulatory effect of the endothelium on blood vessels has been shown to be impaired in atherosclerotic arteries in humans and animals and in animal models of hypertension.

METHODS

To determine whether patients with essential hypertension have an endothelium-dependent abnormality in vascular relaxation, we studied the response of the forearm vasculature to acetylcholine (an endothelium-dependent vasodilator) and sodium nitroprusside (a direct dilator of smooth muscle) in 18 hypertensive patients (mean age [+/- SD], 50.7 +/- 10 years; 10 men and 8 women) two weeks after the withdrawal of antihypertensive medications and in 18 normal controls (mean age, 49.9 +/- 9; 9 men and 9 women). The drugs were infused at increasing concentrations into the brachial artery, and the response in forearm blood flow was measured by strain-gauge plethysmography.

RESULTS

The basal forearm blood flow was similar in the patients and controls (mean +/- SD, 3.4 +/- 1.3 and 3.7 +/- 0.8 ml per minute per 100 ml of forearm tissue, respectively; P not significant). The responses of blood flow and vascular resistance to acetylcholine were significantly reduced in the hypertensive patients (P less than 0.0001); maximal forearm flow was 9.1 +/- 5 ml per minute per 100 ml in the patients and 20.0 +/- 8 ml per minute per 100 ml in the controls (P less than 0.0002). However, there were no significant differences between groups in the responses of blood flow and vascular resistance to sodium nitroprusside. Because the vasodilator effect of acetylcholine might also be due to presynaptic inhibition of the release of norepinephrine by adrenergic nerve terminals, the effect of acetylcholine was assessed during phentolamine-induced alpha-adrenergic blockade. Under these conditions, it was also evident that the responses to acetylcholine were significantly blunted in the hypertensive patients (P less than 0.03).

CONCLUSIONS

Endothelium-mediated vasodilation is impaired in patients with essential hypertension. This defect may play an important part in the functional abnormalities of resistance vessels that are observed in hypertensive patients.

Beneficial and detrimental effects of lidoflazine in microvascular angina

Lidoflazine, a piperazine derivative calcium antagonist, was investigated as therapy in 22 patients with microvascular angina (chest pain, angiographically normal coronary arteries and left ventricle, microvascular constrictor response to pacing after ergonovine administration and limited coronary flow response to dipyridamole). Eighteen of 22 patients reported symptom benefit while taking lidoflazine 360 mg daily. Compared to baseline exercise treadmill testing, lidoflazine resulted in significant improvement in exercise duration (812 +/- 337 vs 628 +/- 357 seconds, p less than 0.01) and time to onset of chest pain (530 +/- 343 vs 348 +/- 246 seconds, p less than 0.01). The 5 patients with ischemic ST-segment changes during baseline testing demonstrated an almost 4-minute delay in ST-segment depression (3 patients) or no ST-segment depression (2 patients) while taking lidoflazine. Repeat invasive study of coronary flow in 11 patients taking lidoflazine demonstrated significantly greater coronary vasodilation at rest, during pacing, during pacing after ergonovine and after dipyridamole administration (all p less than 0.03), compared to the initial drug-free study. During the randomized, placebo-controlled phase of the study with 7-week treatment periods, 9 of 11 patients who completed this phase of the study preferred lidoflazine and all demonstrated improved exercise capacity with lidoflazine compared to placebo. However, 3 patients developed malignant ventricular arrhythmias, and 1 died while taking lidoflazine, resulting in termination of the study. Limited coronary vasodilator response in microvascular angina has a reversible vasoconstrictor component and may be due to elevated systolic calcium levels. Despite the hemodynamic, symptom and exercise benefit, lidoflazine may be unsafe for clinical use because of its propensity to cause potentially fatal ventricular arrhythmias.

Coronary flow reserve, esophageal motility, and chest pain in patients with angiographically normal coronary arteries

PURPOSE AND METHODS

To ascertain the relative prevalence of abnormalities of coronary flow reserve and esophageal function in patients with chest pain despite angiographically normal coronary arteries, 87 patients underwent invasive study of coronary flow reserve and, during the same week, esophageal testing.

RESULTS

Sixty-three of the 87 patients (72%) demonstrated abnormalities of coronary flow reserve, as evidenced by an increase in coronary resistance during the stress of rapid atrial pacing after administration of ergonovine 0.15 mg intravenously (1.33 +/- 0.36 mm Hg.minute/mL), compared with pacing at the same heart rate before ergonovine administration (1.10 +/- 0.33 mm Hg.minute/mL). This higher coronary vascular resistance occurred in the absence of significant epicardial coronary artery luminal narrowing. Fifty-seven of these 63 patients (90%) with a coronary vasoconstrictor response to ergonovine described their typical chest pain during pacing stress, compared with only six of 24 patients (25%) who demonstrated no coronary flow abnormality (p less than 0.001). After administration of dipyridamole 0.5 to 0.75 mg/kg intravenously to 65 patients, the 48 patients with ergonovine-induced vasoconstriction had a significantly higher minimum coronary resistance, compared with the 17 patients without a coronary vasoconstrictor response to ergonovine (0.65 +/- 0.21 versus 0.47 +/- 0.13 mm Hg.minute/mL, p less than 0.03). Twenty of 87 patients (23%) had abnormal esophageal motility [nutcracker esophagus (11), nonspecific motility disorder (seven), and diffuse esophageal spasm (two)], including 16 of the 63 patients (25%) with abnormal coronary flow reserve. Twenty-four (28%) patients experienced their typical chest pain during motility testing, but only five of these patients met criteria for abnormal esophageal motility. Nine of 75 patients tested (12%) had their typical chest pain during Bernstein testing, and 18 of 38 patients (47%) tested had their typical chest pain provoked by intraesophageal balloon distention.

CONCLUSIONS

Seventy-one of 87 patients (82%) with anginal-like chest pain and normal epicardial vessels in our series had a disorder of either coronary flow reserve, esophageal motility, and/or reproduction of typical chest pain during acid infusion. Of interest, chest pain was commonly encountered during cardiac and esophageal testing (85% of patients), regardless of the ability to demonstrate an abnormality of coronary flow reserve or abnormal esophageal function. This suggests that pain experienced by these patients may be a consequence of myocardial ischemia, esophageal dysfunction, abnormal visceral nociception, or a combination of any or all of these entities.

Electrophysiologic abnormalities in patients with hypertrophic cardiomyopathy. A consecutive analysis in 155 patients

Electrophysiologic studies (EPS) were performed in 155 patients with hypertrophic cardiomyopathy (HCM). Indications for EPS were cardiac arrest in 22 patients, syncope in 55 patients, presyncope in 37 patients, asymptomatic ventricular tachycardia (VT) in 24 patients, palpitations in 10 patients, and a strong family history of sudden cardiac death in seven patients. Thirty-five (23%) patients had significant resting left ventricular outflow tract obstruction. Electrophysiologic abnormalities were present in 126 (81%) patients. A high prevalence of abnormal sinus-node function (66%) and His-Purkinje (HV) conduction (30%) was noted. The most commonly induced supraventricular arrhythmias were atrial reentrant tachycardia and atrial fibrillation (10% and 11% of patients, respectively). Accessory atrioventricular pathways were present in seven (5%) patients. Programmed ventricular stimulation (PVS) induced nonsustained ventricular tachycardia in 22 (14%) patients and sustained ventricular arrhythmia in 66 (43%) patients. Sustained ventricular arrhythmia was polymorphic VT in 48 (73%) patients, monomorphic VT in 16 (24%) patients, and ventricular fibrillation in two (3%) patients. Induction was with two premature stimuli in 19 (29%) patients and three premature stimuli in 47 (71%) patients. Of 17 cardiac arrest survivors with sustained ventricular arrhythmia, 16 (94%) patients required three premature stimuli for arrhythmia induction. Sustained ventricular arrhythmia was induced at a right ventricular site in 51 (77%) patients and at a left ventricular site in 15 (23%) patients. Univariate analysis showed a significant (p less than 0.05) association between inducibility of sustained ventricular arrhythmia and VT on Holter in patients with a history of cardiac arrest or syncope but not in patients with presyncope or asymptomatic patients. Multivariate logistic regression analysis revealed that the following were significantly associated with inducibility of sustained ventricular arrhythmia: clinical presentation (cardiac arrest more than syncope more than presyncope more than asymptomatic patients, p = 0.0002; chronic or inducible atrial fibrillation, p = 0.002; and male gender, p = 0.04). In contrast, there was no clinical correlate of induced nonsustained VT.(ABSTRACT TRUNCATED AT 400 WORDS)

A prospective, randomized, controlled trial of prednisone for dilated cardiomyopathy

Although prednisone has been used to treat patients with idiopathic dilated cardiomyopathy, its efficacy has not been rigorously studied. We therefore randomly assigned 102 patients to either treatment with prednisone (60 mg per day) or a control group. At three months, improvement, defined prospectively as an increase in the ejection fraction of greater than or equal to 5 percentage points, was observed in 53 percent of the patients receiving prednisone and 27 percent of the controls (P = 0.005). The mean (+/- SE) ejection fraction increased 4.3 +/- 1.5 percentage points (from 17.9 +/- 1.0 to 22.2 +/- 1.6 percent) in the prednisone group, as compared with 2.1 +/- 0.8 percentage points (from 17.1 +/- 1.1 to 19.3 +/- 1.4 percent) in the control group (P = 0.054). All patients were categorized prospectively in two separately randomized subgroups. "Reactive" patients (n = 60) were those who had fibroblastic (n = 36) or lymphocytic (n = 2) infiltration or immunoglobulin deposition (n = 16) on endomyocardial biopsy, a positive gallium scan (n = 7), or an elevated erythrocyte sedimentation rate (n = 18). "Nonreactive" patients (n = 42) had none of these features. At three months, 67 percent of the reactive patients who received prednisone had improvement, as compared with 28 percent of the reactive controls (P = 0.004). Nonreactive patients did not improve significantly with prednisone (P = 0.51). After three months, reactive patients who received prednisone daily were switched to alternate-day therapy (60 mg every other day), and after six months the improvement seen earlier was no longer present. These data suggest that patients with idiopathic dilated cardiomyopathy may have some improvement when given a high dose of prednisone daily. However, the increases in the ejection fraction that we observed during prednisone treatment were small, their duration was limited, and the side effects were important. Overall, prednisone was judged to have only marginal clinical benefit, and should not be administered as standard therapy for dilated cardiomyopathy.

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)

Long-term outcome of patients with hypertrophic cardiomyopathy successfully resuscitated after cardiac arrest

This study describes the long-term outcome of 33 patients with hypertrophic cardiomyopathy who experienced a cardiac arrest but were successfully resuscitated. Cardiac arrest occurred at ages 9 to 62 years (mean 32); five patients survived multiple (two or three) arrests. A variety of treatments were administered; 18 patients with left ventricular outflow tract obstruction underwent ventricular septal myotomy-myectomy or mitral valve replacement and also received drug therapy; 15 patients received medical therapy alone. To date, 22 (67%) of the 33 patients have survived after the initial cardiac arrest for periods of 17 months to 22 years (mean 7 years); 12 patients have survived for greater than or equal to 5 and 6 for greater than or equal to 10 years. Of the 22 survivors, 16 have remained asymptomatic or only mildly symptomatic over the period of follow-up; 6 others have become severely symptomatic with heart failure, including 3 with evidence of left ventricular wall thinning and cavity enlargement. Eight patients ultimately died of natural cardiac causes (suddenly or of progressive heart failure) 7 months to 8.4 years (mean 4 years) after their initial cardiac arrest. Actuarial patient survival was 97 +/- 3%, 74 +/- 9% and 61 +/- 11% after 1, 5 and 10 years, respectively. Event-free rate (defined as actuarial survival without recurrent cardiac arrest of death) was 83 +/- 7%, 65 +/- 9% and 53 +/- 11%, respectively. For this group of patients with hypertrophic cardiomyopathy who were treated in a nonsystematic fashion with a variety of therapeutic strategies, the long-term outcome after surviving a cardiac arrest was variable.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac norepinephrine kinetics in hypertrophic cardiomyopathy

We examined the uptake and release of norepinephrine in the cardiac circulation and other regional vascular beds in 11 patients with hypertrophic cardiomyopathy (HCM) and in 10 control subjects during simultaneous infusion of tracer-labeled norepinephrine and isoproterenol. Cardiac neuronal uptake of norepinephrine was assessed by comparing regional removal of tracer-labeled norepinephrine with that of tracer-labeled isoproterenol (which is not a substrate for neuronal uptake) and by the relation between production of dihydroxyphenylglycol (DHPG), an exclusively intraneuronal metabolite of norepinephrine, and regional spillover of norepinephrine. Cardiac extraction of norepinephrine averaged 59 +/- 17% in the patients with HCM, significantly less than in the control subjects (79 +/- 13%, p less than 0.05), whereas cardiac extraction of isoproterenol was similar in the two groups (13 +/- 23% versus 13 +/- 14%), indicating that neuronal uptake of norepinephrine was decreased in the patients with HCM. The cardiac arteriovenous difference in norepinephrine was significantly larger in the patients with HCM than in the control subjects (73 +/- 77 versus 13 +/- 50 pg/ml, p less than 0.05), as was the product of the arteriovenous difference in norepinephrine and coronary blood flow (7.3 +/- 7.3 versus 0.8 +/- 3.0 ng/min, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of surgical reduction of left ventricular outflow obstruction on hemodynamics, coronary flow, and myocardial metabolism in hypertrophic cardiomyopathy

To assess the impact of operative reduction of left ventricular outflow obstruction in hypertrophic cardiomyopathy, measurements of great cardiac vein flow, oxygen and lactate content, left ventricular pressures, and cardiac index were measured at rest and during pacing stress in 20 consecutive patients (13, myotomy-myectomy; six, mitral valve replacement; one, both myotomy-myectomy and mitral valve replacement) who underwent both preoperative and postoperative studies. All had angiographically normal epicardial coronary arteries. Operation resulted in reduction in outflow gradient (64 +/- 38 to 4 +/- 7 mm Hg, p less than 0.001) and in left ventricular systolic pressure (186 +/- 32 to 128 +/- 22 mm Hg, p less than 0.001) and was associated with reduction in great cardiac vein flow (101 +/- 26 to 78 +/- 16 ml/min, p less than 0.001) and oxygen consumption in the anterior left ventricle and septum (11.9 +/- 4.1 to 8.4 +/- 1.9 ml O2/min, p less than 0.001) in the basal state. During rapid atrial pacing, 13 of 20 patients experienced chest pain postoperatively, whereas all 20 developed chest pain during preoperative pacing, with an improvement in pacing anginal threshold (or heart rate 150 if no chest pain was experienced) of 16 +/- 18 beats/min (p less than 0.001). The peak great cardiac vein flow (161 +/- 41 to 131 +/- 45 ml/min, p less than 0.025) and myocardial oxygen consumption (19.4 +/- 6.1 to 14.3 +/- 5.5 ml O2/min, p less than 0.005) during pacing, which correlated directly with the severity of the basal left ventricular gradient (p = 0.011 and p = 0.002, respectively), were also reduced by surgery. Lactate metabolism during pacing changed from net production before surgery to net consumption after operation (-17 +/- 47.6 to 4.4 +/- 29.8 mumol/min, p less than 0.01), with six of 20 patients producing lactate after surgery compared with 13 of 20 before surgery (p = 0.06). The six patients with the highest peak great cardiac vein flow (greater than 175 ml/min) during preoperative pacing had greater symptom and metabolic benefit during pacing after surgery compared with the 14 patients with lower peak coronary flow. Postpacing left ventricular end-diastolic pressure (30 +/- 7 to 23 +/- 7 mm Hg, p less than 0.001) and pulmonary artery wedge pressure (24 +/- 6 to 20 +/- 5, p less than 0.001) were reduced after surgery.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium-antagonist receptors in the atrial tissue of patients with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is characterized by a nondilated, hypertrophied left ventricle in the absence of any overt cause. A possible role of adrenergic innervation or of cellular calcium regulation is suggested by the presence of hyperdynamic left ventricular function and by the clinical and symptomatic improvement seen in patients treated with beta-receptor antagonists or calcium antagonists. Therefore, we measured the density of calcium-antagonist receptors and beta-adrenoceptors in the atrial myocardium of 16 patients with hypertrophic cardiomyopathy and 19 patients with various other cardiac disorders. For comparison, we also measured the number of voltage-sensitive sodium channels. Calcium-antagonist binding sites, measured as the amount of dihydropyridine bound to atrial tissue, were increased by 33 percent in patients with hypertrophic cardiomyopathy (mean [+/- SD], 397 +/- 104 fmol per milligram of protein in patients with hypertrophic cardiomyopathy, as compared with 299 +/- 108 in patients with other cardiac disorders; P less than 0.01). The densities of saxitoxin-binding sites on voltage-sensitive sodium channels and beta-adrenoceptors were the same in the two groups, although the density of beta-adrenoceptors was higher in atrial samples from patients receiving beta-receptor antagonists (165 +/- 86 fmol per milligram of protein [patients receiving beta-blockers] vs. 85 +/- 60 [patients not receiving beta-blockers]; P less than 0.04). The increase in the number of calcium-antagonist receptors in hypertrophic cardiomyopathy suggests that abnormal calcium fluxes through voltage-sensitive calcium channels may play a pathophysiologic part in the disease.

Relation between exertional ischemia and prognosis in mildly symptomatic patients with single or double vessel coronary artery disease and left ventricular dysfunction at rest

The randomized multicenter trials indicate that survival in patients with coronary artery disease and left ventricular dysfunction is enhanced by surgical therapy compared with medical therapy. This beneficial effect of coronary bypass surgery was demonstrated in patients with either three vessel or left main coronary artery disease, but not in those with one or two vessel disease. To determine whether subgroups of mildly symptomatic patients with one or two vessel coronary artery disease and left ventricular dysfunction have an increased risk of death or cardiac events during medical therapy, 53 consecutive patients with angiographically defined one or two vessel disease and impaired left ventricular function (ejection fraction 20% to 40%) were studied by exercise electrocardiography (ECG) and rest and exercise radionuclide angiography. All but two patients had previous myocardial infarction, and all were asymptomatic or only mildly symptomatic during medical therapy. By univariate life table analysis, mortality during medical therapy was associated significantly with the ST segment response to exercise (p less than 0.05) and with both the exercise ejection fraction (p less than 0.05) and the magnitude of change in ejection fraction with exercise (p less than 0.005). In patients with an exercise ejection fraction greater than 30%, the probability of survival at 6 years was 97 +/- 3% (+/- SE) compared with a survival rate of 62 +/- 14% in the remaining subjects (p less than 0.005). Similarly, 6 year survival was 100% in patients whose ejection fraction increased from the value at rest but was only 74 +/- 10% in the remaining patients (p less than 0.005). Exercise capacity was not associated with survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrasting effects of verapamil and nifedipine on pH of ischemic myocardium in the dog

It remains unknown whether the actions of verapamil to depress and nifedipine to enhance contractile function of ischemic myocardium influence the degree of myocardial ischemic injury. Thus, we measured intramyocardial pH using fiberoptic pH probes in 43 anesthetized open-chest dogs pretreated for 30 min with verapamil, or nifedipine in doses that decreased aortic pressure 10 to 15 mm Hg before ligation of the left anterior descending coronary artery for 15 min. Drugs were continued during the 15-min ischemic period until the animals were euthanized without reperfusion: verapamil, 10-20 micrograms/kg/min and nifedipine, 2 to 4 micrograms/kg/min i.v. Verapamil-treated dogs showed higher pH of ischemic subendocardium after 15 min ischemia (6.75 +/- 0.07) than did the nifedipine (6.48 +/- 0.04) or placebo (6.43 +/- 0.05) groups, even if the animals were paced (6.71 +/- 0.11) to prevent the negative chronotropic effect of verapamil (P less than 0.01). Neither verapamil nor nifedipine changed collateral myocardial blood flow from 0.10 +/- 0.02 in the subendocardium and 0.17 +/- 0.03 ml/min/g in the subepicardium. Left ventricular function estimated by left ventricular dp/dt was depressed 15% by verapamil and enhanced 26% by nifedipine. Thus, verapamil, but not nifedipine, relieves acidosis of ischemic myocardium after acute coronary occlusion in doses that sustain a 10 to 15 mm Hg decrease in aortic pressure. Nifedipine, in doses that produced the same 10 to 15 mm Hg decrease in mean aortic pressure, did not increase intramyocardial pH, as it enhanced contractile function, estimated by left ventricular dp/dt.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina due to coronary microvascular disease in hypertensive patients without left ventricular hypertrophy

When angina occurs in patients with hypertension, it is usually attributed to coronary artery disease or left ventricular hypertrophy. To determine the contribution of coronary microvascular abnormalities to angina in patients with hypertension, we evaluated hypertensive patients without coronary artery disease or left ventricular hypertrophy by measuring the coronary responses to rapid atrial pacing before and after administration of ergonovine. We compared 12 hypertensive patients who had pacing-induced angina with 13 normotensive subjects without such angina. The two groups had similar coronary flow (in the great cardiac vein) at rest; however, pacing increased coronary flow less in hypertensive patients with angina than in normotensive subjects (48 vs. 83 percent; P = 0.05). In the hypertensive patients with angina, pacing after ergonovine increased coronary flow by only 32 percent (as compared with 48 percent before ergonovine; P less than 0.05) and decreased coronary resistance by 15 percent (as compared with 28 percent before ergonovine; P less than 0.05), indicating the presence of ergonovine-induced vasoconstriction. In normotensive subjects, in contrast, cardiac pacing after ergonovine increased coronary flow by 112 percent (P less than 0.001), and its effect on coronary resistance was not different from that of pacing before ergonovine. The hypertensive patients with angina had a significant increase in myocardial oxygen extraction during pacing after ergonovine and less of an increase in myocardial lactate consumption - a response consistent with the presence of myocardial ischemia. Thus, angina in hypertensive patients without epicardial coronary disease may be caused by myocardial ischemia, which appears to be due to an abnormally elevated resistance of the coronary microvasculature.

Long-term serial changes in left ventricular function and reversal of ventricular dilatation after valve replacement for chronic aortic regurgitation

In most patients with aortic regurgitation, valve replacement results in reduction in left ventricular dilatation and an increase in ejection fraction. To determine the relation between serial changes in ventricular dilatation and changes in ejection fraction, we studied 61 patients with chronic severe aortic regurgitation by echocardiography and radionuclide angiography before, 6-8 months after, and 3-7 years after aortic valve replacement. Between preoperative and early postoperative studies, left ventricular end-diastolic dimension decreased (from 75 +/- 6 to 56 +/- 9 mm, p less than 0.001), peak systolic wall stress decreased (from 247 +/- 50 to 163 +/- 42 dynes x 10(3)/cm2), and ejection fraction increased (from 43 +/- 9% to 51 +/- 16%, p less than 0.001). Between early and late postoperative studies, diastolic dimension and peak systolic wall stress did not change, but ejection fraction increased further (to 56 +/- 19%, p less than 0.001). The increase in ejection fraction correlated with magnitude of reduction in diastolic dimension between preoperative and early postoperative studies (r = 0.63), between early and late postoperative studies (r = 0.54), and between preoperative and late postoperative studies (r = 0.69). Late increases in ejection fraction usually represented the continuation of an initial increase occurring early after operation. Thus, short-term and long-term improvement in left ventricular systolic function after operation is related significantly to the early reduction in left ventricular dilatation arising from correction of left ventricular volume overload. Moreover, late improvement in ejection fraction occurs commonly in patients with an early increase in ejection fraction after valve replacement but is unlikely to occur in patients with no change in ejection fraction during the first 6 months after operation.

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.

Dynamic limitation of coronary vasodilator reserve in patients with dilated cardiomyopathy and chest pain

Twenty-six patients with dilated cardiomyopathy and angiographically normal coronary arteries, 12 of whom gave a history of anginal chest pain, underwent noninvasive and invasive hemodynamic study. During treadmill exercise testing, patients with a history of angina demonstrated worse effort tolerance (7.4 +/- 4.9 versus 13.6 +/- 5.1 minutes, p less than 0.005) and a lower end-exercise systolic blood pressure-heart rate product (17.9 +/- 3.4 versus 23.6 +/- 4.9 mm Hg.beats/min x 10(3), p less than 0.005) compared with patients without a history of angina. During rapid atrial pacing after ergonovine, 0.15 mg intravenously, 11 of the 12 patients with a history of angina experienced their typical chest pain, in contrast to only 1 of 12 patients without a history of angina. The angina group, compared with the nonangina group, had significantly lower great cardiac vein flow (118 +/- 24 versus 160 +/- 43 ml/min, p less than 0.01), and higher coronary resistance (0.87 +/- 0.21 versus 0.66 +/- 0.25 mm Hg.min/ml, p less than 0.05), significant widening of the arterial--great cardiac vein oxygen difference and a significant fall in cardiac index during pacing. Further, ergonovine resulted in higher coronary resistance during pacing in the angina group compared with pacing alone (+0.16 +/- 0.16 mm Hg min/ml, p less than 0.01), in the absence of significant reduction in epicardial coronary artery luminal diameter. After dipyridamole, 0.5 to 0.75 mg/kg intravenously, to 21 patients, the 7 patients with a history of angina had significantly lower flow (149 +/- 37 versus 218 +/- 73 ml/min, p less than 0.05) and higher coronary resistance (0.59 +/- 0.09 versus 0.43 +/- 0.17 mm Hg.min/ml, p less than 0.05) than did the nonangina group. It is concluded that patients with dilated cardiomyopathy and chest pain unrelated to epicardial coronary artery disease exhibit impaired vasodilator responses to both metabolic and pharmacologic stimuli, and an increased sensitivity to the vasoconstrictor effects of ergonovine. Whether these findings are of etiologic or long-term prognostic significance is unknown.

Impaired forearm vasodilator reserve in patients with microvascular angina. Evidence of a generalized disorder of vascular function?

In previous work, we described a group of patients with angina-like chest pain and normal coronary arteries. These patients had impaired coronary vasodilator responses to the stress of rapid atrial pacing and to the administration of dipyridamole, a potent vasodilator of coronary arterioles. This abnormality appears to be localized to the prearteriolar microvascular bed. To determine whether these patients have a more generalized abnormality of vasodilator reserve, we used mercury-in-Silastic strain-gauge plethysmography to compare their hyperemic responses to forearm ischemia with those of normal controls. After 10 minutes of ischemia, peak forearm flow was 39.9 +/- 5.0 ml per minute per deciliter in the controls [corrected] and 31.7 +/- 10.5 in the patients [corrected] (21 percent reduction; 95 percent confidence interval, 4 percent to 37 percent). Flow responses were also significantly reduced after three and five minutes of ischemia. Correspondingly, the vascular resistance after ischemia was also consistently higher in the patients with microvascular angina. The degree of vasodilator impairment in the peripheral circulation correlated well with the degree of vasodilator impairment in the coronary circulation (r = 0.74; P less than 0.004). Thus, patients with microvascular angina appear to have an impairment of vasodilator reserve that affects not only their coronary circulation but also their peripheral arterial bed.

Prognostic implications of symptomatic versus asymptomatic (silent) myocardial ischemia induced by exercise in mildly symptomatic and in asymptomatic patients with angiographically documented coronary artery disease

Patients with coronary artery disease (CAD) may undergo periods of reversible myocardial ischemia without experiencing angina. To study the prognostic implications of "silent" myocardial ischemia induced by exercise, exercise electrocardiography and radionuclide angiography were performed in 131 consecutive patients with CAD, preserved left ventricular (LV) function at rest and mild or no symptoms during medical therapy. All patients who died during medical therapy were in the subgroup of patients with 3-vessel CAD in whom exercise-induced ischemia developed, which was characterized by both a decrease in LV ejection fraction and ST-segment depression. Patients in whom angina pectoris developed during exercise (54% of all patients) had a greater prevalence of this combined ischemic response to exercise than patients without angina (61% vs 27%, p less than 0.001) and also a greater prevalence of left main or 3-vessel CAD (59% vs 25%, p less than 0.001). However, when inducible ischemia was demonstrated, risk stratification and prognosis were the same whether the ischemic episode was symptomatic or silent. Among patients having both a reduction in ejection fraction and a positive ST-segment response, the likelihood of significant left main narrowing (13% vs 26%), 3-vessel CAD (56% vs 51%) and death during subsequent medical therapy (16% vs 9%) was similar in patients with silent compared to those with symptomatic ischemia. These data indicate that patients in whom angina develops during exercise have a greater prevalence of high-risk coronary anatomy and of inducible ischemia than patients without angina. However, once inducible ischemia is documented, the symptomatic response to exercise appears irrelevant for prognostic or risk stratification considerations.

Differences in coronary flow and myocardial metabolism at rest and during pacing between patients with obstructive and patients with nonobstructive hypertrophic cardiomyopathy

Fifty patients with hypertrophic cardiomyopathy underwent invasive study of coronary and myocardial hemodynamics in the basal state and during the stress of pacing. The 23 patients with basal obstruction (average left ventricular outflow gradient, 77 +/- 33 mm Hg; left ventricular systolic pressure, 196 +/- 33 mm Hg, mean +/- 1 SD) had significantly lower coronary resistance (0.85 +/- 0.18 versus 1.32 +/- 0.44 mm Hg X min/ml, p less than 0.001) and higher basal coronary flow (106 +/- 20 versus 80 +/- 25 ml/min, p less than 0.001) in the anterior left ventricle, associated with higher regional myocardial oxygen consumption (12.4 +/- 3.6 versus 8.9 +/- 3.3 ml oxygen/min, p less than 0.001) compared with the 27 patients without obstruction (mean left ventricular systolic pressure 134 +/- 18 mm Hg, p less than 0.001). Myocardial oxygen consumption and coronary blood flow were also significantly higher at paced heart rates of 100 and 130 beats/min (the anginal threshold for 41 of the 50 patients) in patients with obstruction compared with those without. In patients with obstruction, transmural coronary flow reserve was exhausted at a heart rate of 130 beats/min; higher heart rates resulted in more severe metabolic evidence of ischemia with all patients experiencing chest pain, associated with an actual increase in coronary resistance. Patients without obstruction also demonstrated evidence of ischemia at heart rates of 130 and 150 beats/min, with 25 of 27 patients experiencing chest pain. In this group, myocardial ischemia occurred at significantly lower coronary flow, higher coronary resistance and lower myocardial oxygen consumption, suggesting more severely impaired flow delivery in this group compared with those with obstruction. Abnormalities in myocardial oxygen extraction and marked elevation in filling pressures during stress were noted in both groups. Thus, obstruction to left ventricular outflow is associated with high left ventricular systolic pressure and oxygen consumption and therefore has important pathogenetic importance to the precipitation of ischemia in patients with hypertrophic cardiomyopathy. Patients without obstruction may have greater impairment in coronary flow delivery during stress.

Occurrence and significance of progressive left ventricular wall thinning and relative cavity dilatation in hypertrophic cardiomyopathy

This investigation was undertaken to assess the prevalence of systolic dysfunction, left ventricular (LV) wall thinning and cavity enlargement in a large population of patients with hypertrophic cardiomyopathy (HC), and to determine the role of these conditions in the natural history of this disease. Of 217 consecutively studied patients with HC, most of whom were severely symptomatic, 197 (91%) had an LV ejection fraction of 50% or more and 20 (9%) had an ejection fraction of less than 50% as assessed with radionuclide angiography. Changes in LV wall thickness and cavity dimension were evaluated using serial M-mode and 2-dimensional echocardiography over an average follow-up of 3.6 years in 67 of the 217 patients (54 with ejection fraction of greater than or equal to 50% and 13 with ejection fraction less than 50%). A substantial decrease (at least 5 mm) in LV wall thickness was seen in 8 of the 13 patients (62%) with an ejection fraction greater than or equal to 50%, but in only 2 of the 54 patients (4%) with an ejection fraction greater than or equal to 50% (p less than 0.001). LV cavity dimension increased significantly over the period of follow-up in the 13 patients with depressed ejection fraction (from 44 +/- 5 to 49 +/- 7 mm, p less than 0.005); however, absolute cavity size remained normal (less than or equal to 52 mm or less) in 10 of these 13 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Low density lipoprotein modulation of porcine coronary artery contractile response to histamine

Right coronary artery ring segments from miniature swine contracted to histamine with a force and sensitivity comparable to that reported for human right coronary artery ring segments. When the ring segments were suspended in preparations of human low density lipoprotein (LDL) the contractility was reduced. With denuded rings the contractility was significantly lower in the LDL at 1.1 X 10(-4) M histamine. With intact rings significantly less tension was generated in the LDL at concentrations greater than 6 X 10(-5) M histamine. Thus LDL attenuates the contractile response of the porcine right coronary artery to histamine.

Determinants of ventricular arrhythmias in mildly symptomatic patients with coronary artery disease and influence of inducible left ventricular dysfunction on arrhythmia frequency

To determine the relation among ventricular arrhythmias, prognostic factors and reversible ischemia in coronary artery disease, 131 drug-free, minimally symptomatic patients were studied by radionuclide angiography and 24 hour Holter electrocardiographic monitoring. High grade ventricular arrhythmias (couplets, salvos of premature ventricular complexes and R on T phenomenon) were observed in 33 patients (25%) and were related to lower rest and exercise ejection fraction, greater number of stenotic coronary arteries and higher prevalence of regional wall motion abnormalities at rest (all p less than or equal to 0.1). Among patients with subnormal rest ejection fraction, high grade arrhythmias occurred with greater prevalence in those with reversible left ventricular dysfunction (reduction in ejection fraction) during exercise compared with those with a normal ejection fraction response (59 versus 23%, p less than 0.05), a relation observed principally in patients with multivessel disease. These data indicate that in minimally symptomatic patients with coronary artery disease, arrhythmias are related to both extent of disease and severity of regional and global ventricular dysfunction and are most prevalent in patients with ventricular dysfunction and evidence of inducible ischemia, factors indicating poor long-term prognosis during medical therapy.

Three year anatomic, functional and clinical follow-up after successful percutaneous transluminal coronary angioplasty

Because the long-term anatomic effects of percutaneous transluminal coronary angioplasty are unknown, follow-up evaluations including coronary angiography, treadmill exercise testing and rest and bicycle exercise radionuclide angiography were performed in 46 patients 6.3 +/- 2.0 and 37.6 +/- 3.6 (mean +/- SD) months after they had undergone successful single lesion angioplasty. The severity of the coronary stenosis decreased significantly at each evaluation; the mean diameter stenosis was 66 +/- 13% before angioplasty, 30 +/- 13% immediately after and 26 +/- 16% and 19 +/- 13% at 6 months and 3 years, respectively. Exercise time increased from 9.8 +/- 4.4 minutes before angioplasty to 18.3 +/- 4.5 minutes immediately after the procedure and remained at that level at 6 months (20.3 +/- 4.6 minutes) and 3 years (18.2 +/- 4.5 minutes). Left ventricular ejection fraction during exercise decreased 4 +/- 6% compared with rest before angioplasty, but increased 7 +/- 7% immediately after angioplasty and this increase was maintained at 6 months (+/- 6 +/- 7%) and 3 years (+/- 4 +/- 6%). Before angioplasty, 1 patient was in Canadian Heart Association functional class 0, 15 were in class II, 24 in class III and 6 in class IV. Three years later, 25 were in class 0, 10 in class I, 7 in class II and 4 in class III. These results indicate that the short-term anatomic and functional success of coronary angioplasty is maintained for at least 3 years.

Limited coronary flow reserve after dipyridamole in patients with ergonovine-induced coronary vasoconstriction

Patients with anginal chest pain despite angiographically normal coronary arteries and left ventricles may have abnormalities of coronary flow reserve. Twenty-five patients were found to have limited flow reserve during rapid atrial pacing after administration of 0.15 to 0.30 mg iv ergonovine, associated with precipitation of chest pain and hemodynamic and metabolic evidence of myocardial ischemia. No significant narrowing occurred in epicardial coronary artery luminal diameter. An additional 15 patients had no chest pain during pacing; because they developed significantly higher great cardiac vein flow and lower coronary resistance they were considered to have normal vasodilator reserve. After administration of dipyridamole (0.5 to 0.75 mg/kg iv), the lowest absolute levels to which coronary resistance fell (0.79 +/- 0.23 vs 0.47 +/- 0.12 mm Hg X min/ml; p less than .001) and the maximal absolute levels to which great cardiac vein flow rose (134 +/- 34 vs 202 +/- 45 ml/min; p less than .001) were impaired in the 25 patients with ergonovine-induced flow limitation compared with the 15 patients without flow limitation after ergonovine. In addition, 18 of the 25 patients with limited flow reserve after dipyridamole experienced chest pain despite an increase in coronary flow. In these patients, dipyridamole-induced increased flow across small prearteriolar coronary arteries, which were narrowed because of abnormal tonus or sensitivity to vasoconstrictor stimuli, could have resulted in a transmural redistribution of blood flow away from the subendocardium, precipitating subendocardial ischemia. These studies suggest that patients with anginal chest pain despite normal epicardial coronary arteries may have exaggerated coronary responses to vasoconstrictor stimuli, which can result in myocardial ischemia during stress, as well as attenuated responses to coronary vasodilator stimuli.

Intramural ("small vessel") coronary artery disease in hypertrophic cardiomyopathy

Many patients with hypertrophic cardiomyopathy have signs and symptoms of myocardial ischemia and dysfunction. Although hypertrophy and increased left ventricular pressure can account for such abnormalities, altered small intramural coronary arteries have also been described in such patients. To determine the prevalence and extent as well as the clinical relevance of abnormal intramural coronary arteries, a histologic analysis of left ventricular myocardium obtained at necropsy was performed in 48 patients with hypertrophic cardiomyopathy (but without atherosclerosis of the extramural coronary arteries) and in 68 control patients with either a normal heart or acquired heart disease. In hypertrophic cardiomyopathy, abnormal intramural coronary arteries were characterized by thickening of the vessel wall and a decrease in luminal size. The wall thickening was due to proliferation of medial or intimal components, or both, particularly smooth muscle cells and collagen. Of the 48 patients with hypertrophic cardiomyopathy, 40 (83%) had abnormalities of intramural coronary arteries located in the ventricular septum (33 patients), anterior left ventricular free wall (20 patients) or posterior free wall (9 patients); an average of 3.0 +/- 0.7 abnormal arteries were identified per tissue section. Altered intramural coronary arteries were also significantly more common in tissue sections having considerable myocardial fibrosis (31 [74%] of 42) than in those with no or mild fibrosis (31 [30%] of 102; p less than 0.001). Abnormal intramural coronary arteries were also identified in three of eight infants who died of hypertrophic cardiomyopathy before 1 year of age. In contrast, only rare altered intramural coronary arteries were identified in 6 (9%) of the 68 control patients (0.1 +/- 0.05 abnormal arteries per section; p less than 0.001) and those arteries showed only mild thickening of the wall and minimal luminal narrowing. Moreover, of those patients with abnormal intramural coronary arteries, such vessels were about 20 times more frequent in patients with hypertrophic cardiomyopathy (0.9 +/- 0.2/cm2 myocardium) than in control patients (0.04 +/- 0.02/cm2 myocardium). Hence, abnormal intramural coronary arteries with markedly thickened walls and narrowed lumens are present in increased numbers in most patients with hypertrophic cardiomyopathy studied at necropsy and may represent a congenital component of the underlying cardiomyopathic process.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Causes of sudden death in competitive athletes

Cardiovascular diseases responsible for sudden unexpected death in highly conditioned athletes are largely related to the age of the patient. In most young competitive athletes (less than 35 years of age) sudden death is due to congenital cardiovascular disease. Hypertrophic cardiomyopathy appears to be the most common cause of such deaths, accounting for about half of the sudden deaths in young athletes. Other cardiovascular abnormalities that appear to be less frequent but important causes of sudden death in young athletes include congenital coronary artery anomalies, ruptured aorta (due to cystic medial necrosis), idiopathic left ventricular hypertrophy and coronary artery atherosclerosis. Diseases that appear to be very uncommon causes of sudden death include myocarditis, mitral valve prolapse, aortic valve stenosis and sarcoidosis. Cardiovascular disease in young athletes is usually unsuspected during life, and most athletes who die suddenly have experienced no cardiac symptoms. In only about 25% of those competitive athletes who die suddenly is underlying cardiovascular disease detected or suspected before participation and rarely is the correct clinical diagnosis made. In contrast, in older athletes (greater than or equal to 35 years of age) sudden death is usually due to coronary artery disease, and rarely results from congenital heart disease.