Transient transmural reduction of myocardial blood flow demonstrated by thallium-201 scintigraphy, as a cause of variant angina

Coronary Artery Spasm-Related Heart Failure Syndrome: Literature Review

Although heart failure (HF) is a clinical syndrome that becomes worse over time, certain cases can be reversed with appropriate treatments. While coronary artery spasm (CAS) is still underappreciated and may be misdiagnosed, ischemia due to coronary artery disease and CAS is becoming the single most frequent cause of HF worldwide. CAS could lead to syncope, HF, arrhythmias, and myocardial ischemic syndromes such as asymptomatic ischemia, rest and/or effort angina, myocardial infarction, and sudden death. Albeit the clinical significance of asymptomatic CAS has been undervalued, affected individuals compared with those with classic Heberden's angina pectoris are at higher risk of syncope, life-threatening arrhythmias, and sudden death. As a result, a prompt diagnosis implements appropriate treatment strategies, which have significant life-changing consequences to prevent CAS-related complications, such as HF. Although an accurate diagnosis depends mainly on coronary angiography and provocative testing, clinical characteristics may help decision-making. Because the majority of CAS-related HF (CASHF) patients present with less severe phenotypes than overt HF, it underscores the importance of understanding risk factors correlated with CAS to prevent the future burden of HF. This narrative literature review summarises and discusses separately the epidemiology, clinical features, pathophysiology, and management of patients with CASHF.

Coronary Microvascular Spasm: Clinical Presentation and Diagnosis

Professor Maseri pioneered the research and treatment of coronary vasomotion abnormalities represented by coronary vasospasm and coronary microvascular dysfunction (CMD). These mechanisms can cause myocardial ischaemia even in the absence of obstructive coronary artery disease, and have been appreciated as an important aetiology and therapeutic target with major clinical implications in patients with ischaemia with non-obstructive coronary artery disease (INOCA). Coronary microvascular spasm is one of the key mechanisms responsible for myocardial ischaemia in patients with INOCA. Comprehensive assessment of coronary vasomotor reactivity by invasive functional coronary angiography or interventional diagnostic procedure is recommended to identify the underlying mechanisms of myocardial ischaemia and to tailor the best treatment and management based on the endotype of INOCA. This review highlights the pioneering works of Professor Maseri and contemporary research on coronary vasospasm and CMD with reference to endothelial dysfunction, Rho-kinase activation and inflammation.

Myocardial Ischemic Syndromes, Heart Failure Syndromes, Electrocardiographic Abnormalities, Arrhythmic Syndromes and Angiographic Diagnosis of Coronary Artery Spasm: Literature Review

In coronary artery spasm (CAS), an excess coronary vasoconstriction causing total or subtotal vessel occlusion could lead to syncope, heart failure syndromes, arrhythmic syndromes, and myocardial ischemic syndromes including asymptomatic myocardial ischemia, stable and unstable angina, acute myocardial infarction, and sudden cardiac death. Although the clinical significance of CAS has been underrated because of the frequent absence of symptoms, affected patients appear to be at higher risk of syncope, serious arrhythmias, and sudden death than those with classic Heberden's angina pectoris. Therefore, a prompt diagnosis has important therapeutic implications, and is needed to avoid CAS-related complications. While a definitive diagnosis is based mainly on coronary angiography and provocative testing, clinical features may help guide decision-making. We perform a literature review to assess the past and current state of knowledge regarding the clinical features, electrocardiographic abnormalities and angiographic diagnosis of CAS, while a discussion of mechanisms is beyond the scope of this review.

Coronary artery spasm: review and update

Coronary artery spasm (CAS), an intense vasoconstriction of coronary arteries that causes total or subtotal vessel occlusion, plays an important role in myocardial ischemic syndromes including stable and unstable angina, acute myocardial infarction, and sudden cardiac death. Coronary angiography and provocative testing usually is required to establish a definitive diagnosis. While the mechanisms underlying the development of CAS are still poorly understood, CAS appears to be a multifactorial disease but is not associated with the traditional risk factors for coronary artery disease. The diagnosis of CAS has important therapeutic implications, as calcium antagonists, not β-blockers, are the cornerstone of medical treatment. The prognosis is generally considered benign; however, recurrent episodes of angina are frequently observed. We provide a review of the literature and summarize the current state of knowledge regarding the pathogenesis of CAS.

Trends of increasing medical radiation exposure in a population hospitalized for cardiovascular disease (1970-2009)

BACKGROUND

High radiation doses employed in cardiac imaging may increase cancer frequency in exposed patients after decades. The aim of this study was to evaluate the relative trends in medical radiation exposure in a population hospitalized for cardiovascular disease.

METHODS AND RESULTS

An observational single-center study was conducted to examine 16,431 consecutive patients with heart disease admitted to the Italian National Research Council Institute of Clinical Physiology between January 1970 and December 2009. In all patients, the cumulative estimated effective dose was obtained from data mining of electronic records of hospital admissions, adopting the effective dose typical values of the American Heart Association 2009 statement and Mettler's 2008 catalog of doses. Cumulative estimated effective dose per patient in the last 5 years was 22 (12-42) mSv (median, 25(th)-75(th) percentiles), with higher values in ischemic heart disease (IHD), 37 (20-59) vs non-IHD, 13 (8-22) mSv, p<0.001. Trends in radiation exposure showed a steady increase in IHD and a flat trend in non-IHD patients, with variation from 1970-74 to 2005-2009 of +155% for IHD (p<0.001) and -1% in non-IHD (NS). The relative contribution of different imaging techniques was remodeled over time, with nuclear cardiology dominating in 1970s (23% of individual exposure) and invasive fluoroscopy in the last decade (90% of individual exposure).

CONCLUSION

A progressive increase in cumulative estimated effective dose is observed in hospitalized IHD patients. The growing medical radiation exposure may encourage a more careful justification policy regarding ionizing imaging in cardiology patients applying the two main principles of radiation protection: appropriate justification for ordering and performing each procedure, and careful optimization of the radiation dose used during each procedure.

Vasospastic angina assessed by hyperventilation-thallium-201 myocardial scintigraphy

The response to prolonged hyperventilation (HVT) was evaluated by electrocardiography (HVT-ECG) and thallium-201 myocardial scintigraphy (HVT-Tl-Sc) in 40 patients suspected of vasospastic angina. Both tests showed ischaemic changes in 16 patients and no changes in 20 patients. Two patients had abnormal HVT-ECG and normal HVT-Tl-Sc, and the reverse combination was found in two patients. Prolonged HVT was performed in 14 patients during coronary angiography (CAG). Nine developed transient total or subtotal occlusion in one of the major coronary arteries, all of whom had ischaemic HVT-ECG and eight had abnormal HVT-Tl-Sc. In the five patients without spasm at CAG four had normal HVT-ECG and all five normal HVT-Tl-Sc. Our data suggest that HVT-ECG and HVT-Tl-Sc have essentially the same sensitivity and specificity in detecting vasospastic angina.

Role of coronary vasoconstriction in ischemic heart disease and search for novel therapeutic targets

Atherothrombosis has long been recognized as an important mechanism of cardiac events in ischemic heart disease, and large multicenter clinical studies have shown the benefit of antiplatelet agents, statins, beta-blockers and angiotensin converting enzyme inhibitors in preventing these events. However, more recent studies have been less successful at showing incremental gains in targeting these mechanisms, suggesting that the limits of this strategy have been exploited. Coronary vasoconstriction is another important mechanism in ischemic heart disease but has received little attention and yet is a potential therapeutic target. In the current review, the reasons why coronary vasconstriction has received insufficient consideration are explored. In particular, we need to change our approach from lumping heterogeneous clinical entities together to focusing on clinically-discrete homogeneous groups with a common mechanism and thus therapeutic target. The role of coronary vasoconstriction is examined in the various ischemic syndromes (variant angina, chronic stable angina, acute coronary syndromes and syndrome X) and the underlying mechanisms discussed. Finally, in order to advance studies in this field, an innovative research strategy is proposed, including: (1) selection of paradigmatic cases for the various ischemic syndromes; (2) candidate therapeutic targets; and (3) approaches in assessing the clinical efficacy of these potential therapies.

Current clinical features, diagnostic assessment and prognostic determinants of patients with variant angina

BACKGROUND

Clinical characteristics and outcome of patients with variant angina were assessed in the 1970-1980s of the past Century. The recent progress in prevention, diagnosis and treatment of coronary artery disease may have significantly modified clinical characteristics and prognosis of these patients.

METHODS

From January 1991 to December 2002, 202 patients (57.1+/-12 years; 166 men) were diagnosed to have variant angina at our Institute. Detailed clinical findings and clinical events were prospectively collected for each patient.

RESULTS

The median time from the first angina attack to diagnosis was 2 months (range 1-276), with diagnosis requiring >6 months in 31.7% of patients. Coronary angiography (n=183) showed normal coronary arteries in 42.1% of patients and significant coronary stenoses (>50%) in 44.3%, with multi-vessel disease in 8.7%. Diagnosis of variant angina was done during coronary angiography in 3% of cases during the first half of the study period, but in 42% of patients in the second half of the study period. Major cardiac events (MCE, i.e., death, resuscitation from cardiac arrest, myocardial infarction) occurred in 41 patients (20.3%), with 43.9% of events occurring within 1 month of symptom onset. The only variable significantly associated with MCE was the detection during angina of ST segment elevation in both anterior and inferior ECG leads (odds ratio 3.24; 95% confidence interval 1.43-7.36; P=0.005).

CONCLUSION

Our data suggest that variant angina is still a frequently overlooked diagnosis, and a timely diagnosis would be crucial to prevent early life-threatening events. Patients with diffuse ST segment elevation on ECG are those at the highest risk of MCE, independently of angiographic findings.

Coronary microcirculatory vasoconstriction during ischemia in patients with unstable angina

OBJECTIVE

To verify the behavior of coronary microvascular tone during spontaneous ischemia in patients with unstable angina (UA).

BACKGROUND

In UA, the pathogenetic role of vasoconstriction is classically confined at the stenotic coronary segment. However, microcirculatory vasoconstriction has been also suggested by previous experimental and clinical studies.

METHODS

The study included 10 patients with UA (recent worsening of anginal threshold and appearance of angina at rest) and single-vessel CAD. Blood flow velocity was monitored by a Doppler catheter in the diseased artery. Transstenotic pressure gradient was monitored by aortic and distal coronary pressure monitoring. Stenosis resistance was calculated as the ratio between pressure gradient and blood flow, microvascular resistance as the ratio between distal pressure and blood flow. Measurements were obtained at baseline, following intracoronary adenosine (2 mg) and during transient ischemia. Aortic and distal coronary pressures were also measured during balloon coronary occlusion.

RESULTS

Adenosine did not affect stenosis resistance, while it decreased (p < 0.05) microvascular resistance to 52 +/- 22% of baseline. Angina and ischemic ST segment shift were associated with transient angiographic coronary occlusion in 7 of 10 patients; however, in no case was ischemia associated with interruption of flow. Despite markedly different flow values, distal coronary pressure was similar during adenosine and during spontaneous ischemia (48 +/- 15 vs. 46 +/- 20 mm Hg, respectively, NS). During ischemia, a marked increase in the resistance of both coronary stenosis and coronary microcirculation was observed (to 1,233% +/- 1,298% and 671% +/- 652% of baseline, respectively, p < 0.05). Distal coronary pressure was markedly reduced during balloon coronary occlusion (14 +/- 7 mm Hg, p < 0.05 vs. both adenosine and ischemia), suggesting the absence of significant collateral circulation.

CONCLUSIONS

In patients with UA, transient myocardial ischemia is associated with vasoconstriction of both stenotic arterial segment and downstream microcirculation.

[Nuclear cardiology: technical bases and clinical applications]

Although the role of nuclear cardiology is currently well consolidated, the addition of new radiotracers and modern techniques makes it necessary to continuously update the requirements, equipment and clinical applications of these isotopic tests. The characteristics of the radioisotopic drugs and examinations presently used are explained in the first part of this text. In the second, the indications of them in diagnostic and prognostic evaluation of the different coronary diseases are presented.

Coronary Artery Spasm

Attacks of variant angina usually respond promptly to sublingual administration of short-acting nitrates (nitroglycerin, 0.3 to 0.4 mg, or isosorbide dinitrate, 5 to 10 mg), which may be repeated after 3 to 5 minutes if pain persists. In the rare cases resistant to sublingual nitrates, sublingual nifedipine (5 to 10 mg) or, when readily available, intravenous nitrates (nitroglycerin or isosorbide dinitrate, 2 to 10 mg) or calcium antagonists (verapamil, 5 to 10 mg, or diltiazem, 0.15 mg/kg) can be given. All attempts to prevent ischemic attacks by means of specific receptor blockade in patients with vasospastic angina have been unsatisfactory. This may be either because the doses of the blockers used were insufficient or, more likely, because the blockade of a single receptor-agonist interaction leaves receptors for other vasoconstrictor stimuli unopposed and therefore capable of eliciting spasm. Thus, for instance, alpha-adrenergic, serotoninergic, and thromboxane A(2) antagonists all failed to reduce significantly the number of anginal attacks, although they appeared to be effective in some patients. Until the actual causes of the coronary smooth muscle hyperreactivity to constrictor stimuli are known, treatment of vasospastic angina is based on the use of nonspecific vasodilators. Indeed, the mainstay of pharmacologic treatment of coronary artery spasm is calcium channel blocking agents together with nitrates to cover the periods in which spasm is most likely to occur. These powerful vasodilating agents, at their usual doses, are able immediately and completely to control the recurrences of ischemic attacks in as many as 80% of patients. Moreover, some studies have shown that use of calcium antagonists significantly improves clinical outcome in patients with variant angina.

Dipyridamole-induced reversible thallium-201 defect in patients with vasospastic angina and nearly normal coronary arteries

BACKGROUND

Dipyridamole is a vasodilator of resistance vessels and has no vasoconstrictive effect on large coronary arteries.

HYPOTHESIS

The present study used dipyridamole thallium-201 (201Tl) scintigraphy to clarify the role of microvasculature in coronary flow limitation in patients with vasospastic angina and normal coronary arteries.

METHODS

Sixteen patients underwent dipyridamole and exercise 201Tl scintigraphy and provocative coronary angiography with acetylcholine. All patients showed coronary spasm (> 90% vasoconstriction concomitant with ST change) in at least one vessel.

RESULTS

Dipyridamole or exercise caused only ST depression despite the ST elevation observed at spontaneous attack. Dipyridamole 201Tl scintigraphy demonstrated the reversible defects (11 cases), as did exercise 201Tl scintigraphy (13 cases). The region of 201Tl defect was not always consistent with the territories of angiographically depicted vasospastic arteries. Basal coronary tone, assessed by percentage of diameter change of epicardial arteries from baseline to isosorbide dinitrate administration, did not differ between the positive and the negative defect regions.

CONCLUSION

These results support the hypothesis that, in addition to epicardial coronary spasm, the dysfunction of microvasculature is responsible for abnormal coronary perfusion in the subgroup of patients with vasospastic angina and normal coronary arteries.

Super-normal 201Tl retention in hibernating myocardium: an ex-vivo study using the failing human heart

OBJECTIVE

Although the relationship between delayed 201Tl distribution and blood flow in acutely ischemic and infarcted myocardium has been widely explored in the experimental setting, its behaviour in chronically hypoperfused dysfunctioning human myocardium has not yet been evaluated.

METHODS

In tissue samples of excised failing hearts taken from ischemic (IHD) patients and idiopathic dilated cardiomyopathy (IDC) controls, we evaluated the relationship between delayed 201Tl retention (4 h redistribution), blood flow (assessed by means of 99mTc-labelled human albumin microspheres injected during transplantation) and biochemically-assessed fibrosis. 201Tl activity was expressed as the percent of the activity in the region with highest flow and the least fibrosis.

RESULTS

Fibrosis and 201Tl activity were inversely related (r = -0.62, P = 0.0001). In IDC controls, low flows corresponded to uniformly preserved 201Tl retention. In IHD, 46 segments with flows < or = 0.60 ml.min-1.g-1 and 20 segments with flows > 0.60 ml.min-1.g1 showed matching delayed 201Tl retention and flow values; in the remaining 27, there was a disproportionately high tracer accumulation in comparison with flow (flow/201Tl mismatch). Despite significantly less fibrosis and lower flows, the mismatch segments showed significantly greater. 201Tl activity than the segments with concordantly high tracer retention and flow values. Conversely, at equivalent flow rates, the mismatch regions had less fibrosis than the areas with concordantly depressed 201Tl activity and perfusion.

CONCLUSIONS

This super-normal 201Tl retention in hibernating myocardium may indicate a mechanism of cell adaptation to chronic hypoperfusion.

Intra- and postoperative myocardial ischemia without significant coronary artery stenosis

A 73-year-old man without a history of coronary artery disease had two episodes of significant ST-segment elevation indicative of inferior myocardial ischemia during the resection of an abdominal aortic aneurysm. During the further course, sudden ST-segment elevations occurred and resolved spontaneously without preceding hemodynamic instability. The patient sustained two episodes of cardiac arrest due to ventricular fibrillation and intermittent third-degree atrioventricular block with ventricular asystole. On cardiac catheterization, coronary arteries had a right dominant pattern. The right coronary artery was entirely patent on multiple injections. Thus, right coronary artery spasm is the only possible explanation for these observations.

Ergonovine-induced alterations in coronary flow velocity preceding onset of occlusive spasm in patients without significant coronary artery stenoses

This study examined serial changes in coronary flow velocity to elucidate the dynamic change of coronary circulation during coronary spasm. Twenty patients with variant angina and 27 control patients were studied. Coronary flow velocity was monitored using a Doppler guidewire following intracoronary ergonovine administration. In the control group, diastolic flow velocity either did not change or increased slightly in response to ergonovine. However, in patients with variant angina, 2 patterns of flow velocity alterations were observed. In the first pattern, flow initially increased and then suddenly decreased (16 of 20 patients). In the second pattern, flow gradually decreased (3 of 20 patients). In the remaining patient, the coronary flow alteration could not be detected because of branch spasm. When abnormally high flow velocity was defined as a 100% increase in flow after ergonovine administration within 1 minute, and abnormally low flow velocity was defined as a 50% decrease in flow to diagnose variant angina, sensitivities of 35%, 75%, and 85% were noted if flow was measured 1.0, 2.0, and 3.0 minutes after ergonovine administration, respectively. These abnormal flow velocities were observed before ischemic ST changes appeared. In conclusion, in patients with variant angina, characteristic serial changes in coronary flow velocity occur before occlusive spasm. Variant angina may be diagnosed earlier by monitoring flow velocity rather than by monitoring for ischemic electrocardiographic changes.

[Coronary spasm--a clinically relevant problem?]

Coronary spasms are defined as reversible coronary stenosis, which limits coronary blood flow under resting conditions. The demonstration of either spontaneous or provoked coronary spasm proves coronary hypercontractility and thus the diagnosis of variant angina. Several stimuli can provoke coronary vasospasm, but the highest sensitivity and specificity has been shown with ergonovine. Alternatively acetylcholine or with less sensitivity, but high specificity, hyperventilation may be employed. Typically coronary vasospasm presents with angina pectoris at rest; the manifestation with myocardial infarction or syncope are of great clinical importance. The prevalence of the disease is unknown due to the rarely performed provocation tests in Western countries. The incidence of positive test results strongly depends on the symptoms of the patients; from 0% in patients without any evidence for myocardial ischemia up to 54% in patients with typical angina at rest have been observed. Coronary vasospasm is closely related to atherosclerotic coronary artery disease, since intravascular ultrasound studies reveal atherosclerotic plaques in almost any spastic segment. Risk factors for coronary artery disease and coronary vasospasm, however, differ profoundly. For the latter cigarette smoking is the only established risk factor. Although several candidates and predisposing factors (serotonin, histamine, thromboxane, endothelin) have been described, the mediators and the pathogenesis of the disease remains unknown. Endothelial dysfunction alone is not sufficient to explain the features of variant angina. Some evidence supports the hypothesis of local inflammation. The mortality in variant angina depends on the extent of the coronary artery disease. Pure coronary vasospasm does not lead to increased mortality; patients with highly active disease presenting with syncope may have an increased risk. Medical treatment should include long-acting calcium antagonists or nitrates, beta-blockers may even favor the occurrence of ischemic attacks. Although the benefit has not been proven, the use of aspirin may considered in highly active disease.

The Psychophysiological Investigations of Myocardial Ischemia (PIMI) study: objective, methods, and variability of measures

OBJECTIVE

This study evaluated physiological, neuroendocrine, and psychological status and functioning of patients with coronary artery disease in order to clarify their role in the expression of symptoms during myocardial ischemia (MI), and to establish repeatability of responses to mental stress. Design and methods of the study are presented.

METHODS

One hundred ninety-six coronary artery disease patients were examined during physical and mental stress tests in four hospitals. Eligibility criteria included narrowing of at least 50% in the diameter of at least one major coronary artery or verified history of myocardial infarction, and evidence of ischemia on an exercise treadmill test. Psychological, biochemical, and autonomic function data were obtained before, during, and after exposure to mental and exercise stressors during 2 or 3 half-days of testing. Ventricular function was assessed by radionuclide ventriculography, and daily ischemia by ambulatory electrocardiography. Sixty patients returned for a short-term mental stress repeatability study. Twenty-nine individuals presumed to be free of coronary disease were also examined to establish reference values for cardiac responses to mental stress.

RESULTS

Study participants were 41 to 80 years of age; 83 (42%) had a history of MI, 6 (3%) of congestive heart failure, and 163 (83%) of chest pain; 170 (87%) were men; and 90 (46%) had ischemia accompanied by angina during exercise treadmill testing. Ischemia during ambulatory monitoring was found in 35 of 90 (39%) patients with and 48 of 106 (45%) patients without angina during exercise-provoked ischemia. Intraobserver variability of ejection fraction changes during bicycle exercise and two mental stress tests (Speech and Stroop) was good (kappa = 1.0, .90, and .76, respectively; percent agreement = 100, 97.5, and 93.8%, respectively). Variability of assessed wall motion abnormalities during bicycle exercise was better (kappa, agreement = 85%) than during Speech or Stroop kappa and .57, percent agreement = 70% and 82.5%, respectively).

CONCLUSIONS

Study design, quality control data, and baseline characteristics of patients enrolled for a clinical study of symptomatic and asymptomatic myocardial ischemia are described. Lower repeatability of reading wall motion abnormalities during mental stress than during exercise may be due to smaller effects on wall motion and lack of an indicator for peak mental stress.

Spontaneous coronary artery spasm documented in a young woman. A case report

A 35-year-old woman with coronary risk factors presented with nonexertional atypical burning chest pain of 1 week's duration. A myocardial perfusion study with Tc-99m MIBI revealed a severe stress induced anteroseptal perfusion defect that completely reperfused on a subsequent resting Tc-99m MIBI study. Coronary angiography showed mild nonobstructive coronary artery disease. At the termination of the procedure, a spontaneous episode of burning chest pain occurred. Left main coronary artery reinjection of contrast revealed proximal diffuse left anterior descending coronary artery spasm. The patient was followed for 2 years with no further episodes of chest pain, while on calcium channel-blocker medication. The phenomenon of vasospastic angina and the role of myocardial perfusion scintigraphy is discussed.

Induction of polymorphic ventricular tachycardia by programmed ventricular stimulation in vasospastic angina pectoris

This study was designed to examine the ventricular vulnerability of patients with vasospastic angina. Fourteen patients (mean age 57 +/- 9 years) with vasospastic angina underwent electrophysiologic testing during the asymptomatic phase (baseline) and after the relief of acetylcholine-induced spasm with isosorbide dinitrates. Twenty patients without structural heart disease served as a control group. By programmed ventricular stimulation, polymorphic ventricular tachycardia (VT) was induced at baseline in 6 of 14 patients, with 1 patient developing ventricular fibrillation and 7 of 14 patients developing repetitive ventricular responses. After isosorbide dinitrate, polymorphic VT was induced in only 1 patient who had ventricular fibrillation at baseline. Repetitive ventricular responses were induced in 3 of 5 patients who had VT at baseline and in 4 of the 7 patients with repetitive ventricular responses at baseline. There was a significant difference in the incidences and severity of induced ventricular arrhythmias between the 2 phases (p <0.01). Among 20 control subjects, repetitive ventricular responses were induced only in 6 patients, but no VT was induced. There was a significant difference in the incidence of induced ventricular arrhythmias and VT at baseline between the vasospastic angina and control groups (p <0.001 and <0.01, respectively). Thus, patients with vasospastic angina had increased ventricular vulnerability, even during the symptom-free period without ischemic events, which could predispose to the development of life-threatening arrhythmias aggravated by vasospastic attacks.

Pacing-induced ST segment deviation in patients with unstable angina: clinical, angiographic, and hemodynamic correlation

To assess the clinical, coronary arteriographic, and hemodynamic differences between the unstable angina patients manifesting ST segment depression and those showing ST segment elevation as well as those demonstrating chest pain only without ST segment deviation during pacing, low-dose digital subtraction ventriculography was performed in 33 patients before and after abrupt cessation of atrial pacing during selective coronary arteriography. Transient ST segment depression during pacing was observed in 17 patients (52%), whereas 6 patients (18%) showed ST segment elevation; however, 10 patients (30%) did not manifest any ST segment deviation in spite of typical chest pain. Hypertension and a history of myocardial infarction were observed in a significantly higher (P < 0.05) proportion of patients with ST segment depression than in those with ST elevation. Patients who manifested ST segment depression during pacing had a higher incidence of triple-vessel disease (65 vs 17%; P < .05) as compared with the patients with ST segment elevation. Indirect evidence of intracoronary thrombi (complicated lesion, abrupt occlusion, and intraluminal filling defect) was noticed in a higher frequency (P < 0.05) in the group of patients with ST elevation during pacing. In patients with ST segment depression, no significant changes of global left ventricular (LV) functional parameters were observed. However, the length of the LV severe hypokinetic region was increased significantly (6.2 +/- 3.1 vs 23.5 +/- 6.2%; P < 0.005) during pacing in this group of patients. The shortening of the affected segments of the left ventricle was decreased significantly (52.3 +/- 3.6 vs 38.3 +/- 4.9%; P < 0.05) in these patients during pacing. In the group of patients with ST segment elevation during pacing, decrease in ejection fraction was associated with significant (P < 0.01) increase in midwall equatorial diastolic stress as compared with the patients with pacing-induced ST segment depression as well as patients without ST segment deviation. In the group of patients without ST segment deviation during pacing there was no considerable aggravation of LV global or regional function. This distinction should be taken into consideration in evaluating patients with unstable angina for diagnostic and therapeutic intervention.

Myocardial perfusion imaging for evaluating interventions in coronary artery disease

Myocardial perfusion imaging provides a means for evaluating the effects of interventional therapy in several groups of patients with coronary artery disease. In patients with unstable angina, imaging during or after chest pain can be used to identify areas of jeopardized myocardium and to predict the risk of subsequent cardiac events including myocardial infarction. In patients with acute myocardial infarction, the effect of thrombolytic therapy can be monitored, and in patients with chronic ischemia and left ventricular dysfunction, thallium imaging can be used to predict whether revascularization will improve myocardial function. In patients with stable coronary artery disease, perfusion imaging has been used to evaluate efficacy of anti-anginal medications. This article reviews the use of myocardial perfusion imaging in determining the need for, and success of, various medical and surgical therapeutic interventions in patients with ischemic heart disease.

Technetium-99m sestamibi myocardial perfusion imaging in the emergency room evaluation of chest pain

OBJECTIVES

The purpose of this investigation was to evaluate the practicality and short-term predictive value of acute myocardial perfusion imaging with technetium-99m sestamibi in emergency room patients with typical angina and a normal or nondiagnostic electrocardiogram (ECG).

BACKGROUND

Accuracy of emergency room chest pain assessment may be improved when clinical and ECG variables are used in conjunction with acute thallium-201 myocardial perfusion imaging. Technetium-99m sestamibi is a new radioisotope that is taken up by the myocardium in proportion to blood flow, but unlike thallium-201, it redistributes minimally after injection. Technetium-99m sestamibi can thus be injected during chest pain, and images acquired 1 to 2 h later (when patients have been clinically stabilized) will confirm whether abnormalities of perfusion were present at the time of injection.

METHODS

One hundred two emergency room patients with typical angina (on the basis of a standardized angina questionnaire) and a normal or nondiagnostic ECG had a technetium-99m sestamibi injection during symptoms and were followed up for occurrence of adverse cardiac events (cardiac death, nonfatal myocardial infarction, coronary angioplasty, coronary surgery or coronary thrombolysis).

RESULTS

Univariate predictors of cardiac events included the presence of three or more coronary risk factors (p = 0.009, risk ratio 3.3) and an abnormal or equivocal acute technetium-99m sestamibi scan (p = 0.0001, risk ratio 13.9). Multivariate regression analysis identified an abnormal perfusion image as the only independent predictor of adverse cardiac events (p = 0.009). Of 70 patients with a normal perfusion scan, only 1 had a cardiac event compared with 15 patients with equivocal scans or 17 patients with abnormal scans, with a cardiac event rate of 13% and 71%, respectively (p = 0.0004).

CONCLUSIONS

Initial myocardial perfusion imaging with technetium-99m sestamibi when applied in emergency room patients with typical angina and a normal or nondiagnostic ECG appears to be highly accurate in distinguishing between low and high risk subjects.

Non-invasive assessment of residual viability in post-myocardial infarction patients. Role of nuclear techniques

The failure of non-imaging techniques in identifying viable segments has favoured the clinical application of nuclear imaging. The main pathways that support radionuclide imaging are cell membrane integrity, persistence of intermediary metabolism and demonstration of a residual coronary reserve. Thallium-201 reinjection or rest protocols allow the identification of viable myocardium in most of patients with wall motion abnormalities and appear to be the most diffuse, low-cost and available method to detect viable myocardium. More complex approaches use positron emission tomography and matched flow/metabolic information. Flow/metabolic 'mismatch' usually identifies most of hypoperfused regions that show post-operative improvement of regional wall motion. The last promising approach is represented by the demonstration of a maintained regional coronary reserve in dyssynergic areas. Technetium-99m-microspheres (or Teboroxime in the future) can be successfully used for this purpose. The clinical application of radionuclides appears to be one of the principal imaging tools able to identify residual viability.

Reverse redistribution on Tl-201 SPECT images after reperfusion therapy for acute myocardial infarction: possible mechanism and prognostic implications

So-called reverse redistribution on stress Tl-201 imaging has been reported previously, but its significance and clinical implications are not well understood. In patients who received reperfusion therapy for acute myocardial infarction, we frequently observed reverse redistribution on stress Tl-201 images. To investigate the significance of reverse redistribution, 61 patients who underwent reperfusion within 4 h of the onset of chest pain underwent submaximal exercise Tl-201 imaging 3 weeks later. We performed simultaneous coronary arteriography and left ventriculography. We divided these 61 patients into three groups based on the pattern of Tl-201 images. Reverse redistribution was found in 19 patients (Group A), 12 patients had redistribution (Group B), and 30 patients had nonreversible defects (Group C). All patients in Group A had less residual stenosis than those in the other groups, and showed significant improvement of left ventricular function. Furthermore, 12 patients (Group A) demonstrated reverse redistribution or a normal pattern in a follow-up study performed 12 months later. However, in the delayed images the defect was smaller than that shown in the previous study. None of the patients had any symptoms and all returned to their previous occupations. In conclusion, reverse redistribution was common in patients undergoing reperfusion therapy for acute myocardial infarction, especially those with little residual stenosis. Reverse redistribution appears to indicate improved regional wall function in such patients.

A study on coronary hemodynamics during acetylcholine-induced coronary spasm in patients with variant angina: endothelium-dependent dilation in the resistance vessels

The epicardial coronary artery of patients with variant angina is hyperreactive to the constrictive effect of acetylcholine, but it is not known whether the coronary microvasculature also constricts in response to acetylcholine. Incremental doses of acetylcholine were injected into the left coronary artery of 57 patients with variant angina and with spasm in this artery. By measuring coronary sinus blood flow, coronary hemodynamic status just before angiographic documentation of spasm was examined. Acetylcholine induced spasm in the left coronary artery in all patients. It also decreased the diameter of the nonspasm artery by 36 +/- 19% from baseline. For all patients, coronary sinus blood flow was 89 +/- 38 ml/min at baseline and increased to 104 +/- 61 ml/min during an acetylcholine-induced anginal attack (p less than 0.01). In 10 patients with spasm in both the left anterior descending and left circumflex arteries (that is, multivessel spasm), coronary sinus blood flow decreased from 84 +/- 21 to 52 +/- 26 ml/min (p less than 0.01). In the other 47 patients with spasm in only one of these two arteries (that is, single-vessel spasm), coronary sinus blood flow increased from 90 +/- 41 to 115 +/- 61 ml/min (p less than 0.01) without change in the rate-pressure product. It is concluded that in patients with variant angina, acetylcholine induces spasm and constriction in the epicardial coronary artery, whereas it dilates the resistance vessels presumably through the release of the endothelium-dependent relaxing factor.

Technetium-99m sestamibi tomography in patients with spontaneous chest pain: correlations with clinical, electrocardiographic and angiographic findings

The sensitivity and specificity of technetium-99m hexakis-2-methoxy-2-isobutyl-isonitrile (sestamibi) single-photon emission computed tomographic (SPECT) imaging for the diagnosis of coronary artery disease were studied in 45 patients admitted to the hospital for clinical suspicion of unstable angina. Only patients without prior myocardial infarction were included and all patients had technetium-99m sestamibi injection and a 12-lead electrocardiogram (ECG) during and less than or equal to 4 h after an episode of chest pain. Coronary angiography performed in all patients during hospitalization showed significant coronary artery disease (greater than or equal to 50% luminal diameter reduction) in 26 of the 45 patients. The SPECT studies obtained after injection of technetium-99m sestamibi during an episode of spontaneous chest pain showed a sensitivity of 96% for the detection of coronary artery disease; the 12-lead ECG obtained at the time of the injection had a sensitivity of 35%. With the patient in the pain-free state, respective sensitivity values were 65% and 38%. Specificity for the radionuclide study was 79% during pain and 84% in the pain-free state; for the ECG, it was 74% both during and between episodes of pain. The site of the perfusion defect corresponded to the most severe coronary artery lesion in 88% of patients. The severity of the perfusion defect correlated with the extent of coronary artery disease: the defect score was 5.3 +/- 3.3 with one-vessel disease, 4.9 +/- 2.8 with two-vessel disease and 10.5 +/- 5.0 with three-vessel disease (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary artery spasm and vascular biology. Cholinergic constriction

Coronary artery spasm is undoubtedly one of the causative factors of ischemic heart disease, particularly variant-type angina pectoris and myocardial infarction, but the disease mechanisms involved are still unclear. The present review describes the clinical background of coronary artery spasm in relation to ischemic heart disease, including a brief history of studies in this field, and also suggests future guidelines for experimental investigations based on the characteristics of coronary artery spasm, focusing particularly on data we have obtained in our laboratory from studies of cholinergic constriction. The pig may be a suitable animal in which coronary artery spasm could be provoked with cholinergic agents following endothelial denudation. The use of such large animals would allow the study of spastic arterial segments by various methods with angiographic confirmation. After endothelial denudation it is possible that phenotypic changes in cholinergic receptors might occur in smooth muscle cells, and that such changes might remain even after endothelial repair.

Detection and assessment of unstable angina using myocardial perfusion imaging: comparison between technetium-99m sestamibi SPECT and 12-lead electrocardiogram

Forty-five studies using technetium-99m (Tc-99m) sestamibi single photon emission computed tomography (SPECT) were performed on patients hospitalized for spontaneous chest pain suggestive of myocardial ischemia. The studies were done after an injection during an episode of chest pain and a repeated injection when the patients were free of pain. All patients were hospitalized with a presumed diagnosis of unstable angina, and none had evidence of a previous myocardial infarction. The presence of a perfusion defect observed with Tc-99m sestamibi injected during chest pain had a 96% sensitivity and a 79% specificity for the detection of significant coronary artery disease (stenosis greater than or equal to 50%) on subsequent angiography. When the criterion of a larger perfusion defect during pain compared to absence of pain was used, the sensitivity was 81% and the specificity was 84%. In contrast, transient electrocardiographic ischemic changes during pain had a sensitivity of 35% and a specificity of 68%; electrocardiographic changes during or outside episodes of chest pain had a sensitivity of 65% and a specificity of 63% for the diagnosis. Tc-99m sestamibi SPECT represents a reliable noninvasive diagnostic tool that could aid in the diagnosis of myocardial ischemia in patients with spontaneous chest pain and provide additional information to that provided by the electrocardiogram.

Dissociation of exercise tolerance and total myocardial ischemic burden in chronic stable angina pectoris

Exercise treadmill tests and ambulatory monitoring were used in a double-blind, placebo-controlled, double-dummy crossover comparison of nifedipine (10 mg, 3 times daily) and transdermal nitroglycerin (15 mg). All patients (n = 20) had chronic stable angina with symptomatic and silent events. All patients had 3 episodes of angina/week and 3 episodes of ischemia/24 hr. The protocol was made up of 2 weeks of placebo followed by 2 weeks of active drug, then crossed over for 2 weeks of placebo followed by the other active drug. At the end of each 2-week period, patients had ambulatory monitoring and exercise treadmill testing. All ambulatory monitoring reports were read blind and entered into an independent data base. The results were the following: on transdermal nitroglycerin, the duration of ischemia decreased by 57% from 140 min/24 hr to 60 min/24 hr (p = 0.0054). The exercise time increased by 5.5% from 4.8 to 5.0 minutes (p = 0.16). With nifedipine, the duration of ischemia decreased by 22% from 175 min/24 hr to 137 min/24 hr (p = 0.16). The exercise tolerance time increased by 13% from 4.5 to 5.0 minutes (p = 0.0264). Nifedipine increased exercise time without altering total ischemic time, while transdermal nitroglycerin decreased total ischemic time without increasing exercise time. Thus, changes in exercise time do not necessarily predict changes in total ischemic time.

A look at 15 years of planar thallium-201 imaging

Extensive experience has been accumulated over the past 15 years regarding planar thallium-201 imaging. Quantitation of technically superior images provides a high sensitivity and specificity for the detection of CAD. In addition, planar thallium-201 images provide very important prognostic information in different clinical situations. Although single photon emission computerized tomography offers potential theoretical advantages over planar imaging, because of the problems involved in reconstruction, specifically the creation of artifacts, it may not be the ideal imaging modality in all situations. Good quality planar thallium-201 imaging still has an important role in clinical cardiology today.

Study of ridazolol on isolated canine and human coronary arteries

Experiments were performed on isolated canine and human coronary arteries to study the alpha- and beta-adrenolytic properties of ridazolol. On canine coronary arteries precontracted with prostaglandin F2 alpha 2 microM and pretreated with phentolamine 1 microM, ridazolol competitively antagonized the isoproterenol-induced relaxations, with a pA2 value of 8.5 (7.8-9.1). Thereafter the alpha-adrenolytic activity of ridazolol was assessed on these same canine coronary vessels. Ridazolol activity was compared with that of prazosin on dose-response curves to norepinephrine in the presence of cocaine (30 microM) and propranolol (3 microM). Schild plots for both drugs gave straight lines, with slopes not different from unity. The pA2 value was 7.1 (6.8-7.3) for ridazolol and 8.1 (7.9-8.4) for prazosin. In another set of experiments the alpha-adrenolytic activity of ridazolol was compared on canine and human coronary arteries. A submaximal contraction with norepinephrine (10 microM) was first assessed in the presence of propranolol 3 microM. The addition of ridazolol 3 microM significantly decreased the norepinephrine (10 microM)-induced contractions of both preparations. However, the inhibition was more pronounced on canine coronary arteries. In conclusion, ridazolol is a potent beta-adrenergic antagonist with moderate alpha-adrenolytic activity. The weaker inhibition of the norepinephrine-induced contraction observed in human preparations suggests the presence of a heterogeneous population of postjunctional alpha adrenoceptors.

Continuous monitoring of left ventricular function by an ambulatory radionuclide detector in patients with coronary artery disease

Global left ventricular function and a modified V5 electrocardiographic (ECG) lead were continuously monitored by a radionuclide recorder in 12 normal subjects and 39 patients with coronary artery disease while the subjects were performing various daily activities. The ambulatory studies revealed that walking on a level surface caused 11 of 12 normal subjects and 18 of 32 patients to increase their left ventricular ejection fraction by greater than 6% units. A transient decrease in left ventricular ejection fraction (6 to 18%) lasting greater than or equal to 1 min was observed on 36 occasions in 16 patients with coronary artery disease; 12 episodes were accompanied by chest pain or shortness of breath and 24 were asymptomatic. Electrocardiographic ST segment depression suggestive of ischemia was recorded in 6 of the 12 symptomatic and 5 of the 24 asymptomatic episodes. In 10 of the 12 symptomatic episodes, left ventricular ejection fraction began to decrease 30 to 90 s before the onset of symptoms. These studies suggest that continuous monitoring of both left ventricular function and the ECG may permit stratification of episodes of ST depression suggesting ischemia by the degree of left ventricular dysfunction they produce.

Electrocardiographic manifestations and in-hospital prognosis of transient acute myocardial ischemia at rest

From January 1970 to June 1985, transient electrocardiographic changes at rest were documented in 652 patients admitted to our coronary care unit. Patients were stratified according to the type of electrocardiographic alteration at rest: 295 had ST-segment elevation (group 1), 106 T-wave changes (group 2) and 251 ST-segment depression (group 3). Patients in group 3, compared with groups 1 and 2, were more likely to have symptoms of coronary artery disease dating back many years (p less than 0.01 and p less than 0.01, respectively), a previous myocardial infarction (p less than 0.05 and difference not significant), a positive exercise test (p less than 0.01 and p less than 0.01), transient ST-T changes occurring in a higher number of electrocardiographic leads (p less than 0.01 and p less than 0.01), multivessel disease (p less than 0.001 and p less than 0.01) and poor ventricular function (p less than 0.01 and p less than 0.05). Despite these differences, the occurrence of acute myocardial infarction and cardiac death during hospitalization was much more frequent in group 1 compared with groups 2 (p less than 0.02) and 3 (p less than 0.05). However, death occurred in those patients who had poor ventricular function and severe atherosclerosis. A greater susceptibility of group 1 patients to severe vasoconstriction documented by the ergonovine test and by the occurrence of spontaneous spasm seems to account for different in-hospital outcome.

Role of nitrates in silent myocardial ischemia

Assessment of systemic and coronary hemodynamics, myocardial metabolic and mechanical function and scintigraphic and electrocardiographic studies has provided ample evidence for the existence of asymptomatic silent myocardial ischemia in both acute and chronic coronary artery syndromes. There is growing evidence to suggest that a primary decrease in coronary blood flow, resulting from increased coronary arterial resistance, is the principal cause for spontaneous symptomatic and asymptomatic myocardial ischemia in these patients. The precise mechanism for increased coronary arterial resistance has not been clarified, and it is likely to be different in different angina syndromes but similar for both symptomatic and asymptomatic myocardial ischemia. Since nitroglycerin and nitrates can decrease coronary arterial tone and coronary artery resistance, as well as myocardial oxygen requirements, these agents have the potential to relieve episodes of silent myocardial ischemia in patients with coronary artery syndromes.