Prognostic significance of silent ischemia

Exercise-induced right ventricular cardiomyopathy in an endurance cyclist: a case report

Background

The wide-ranging benefits of frequent and moderate exercise are well recorded in the literature. Chronic deleterious remodelling in response to exercise is less well described. We describe an amateur endurance cyclist who, in addition to developing a heart failure syndrome and electrocardiographic evidence of arrhythmia, also developed severe functional tricuspid regurgitation.

Case summary

After developing palpitations during long distance cycle rides as part of his fitness regimen, a 69-year-old male presented to emergency services but was discharged. While continuing to enjoy long-distance cycling, he began to develop peripheral swelling and presented for a second time to hospital. Subsequent investigation found he had a dilated right heart, exercise-induced arrhythmia, and mid-wall myocardial fibrosis. A diagnosis of exercise-induced cardiomyopathy was made. He was managed with diuretics and immediate cessation of exercise. His symptoms improved and he remains symptom free.

Discussion

The volume of blood passing through the right heart increases during exercise. In vulnerable individuals undertaking frequent endurance exercise, this can promote structural remodelling and fibrotic change. It is unclear if cessation of exercise can reverse the remodelled heart. There are some early advances in predictive biomarkers and imaging techniques in categorizing those in the population who would be at risk of developing this cardiomyopathy, and those who can undergo intense exercise regimens without concern. If those at risk of developing an exercise-induced cardiomyopathy can be accurately identified, the next dilemma is how can their risk of heart failure or sudden death be acceptably minimized.

Myocardial perfusion scintigraphy in asymptomatic diabetic patients: a critical review

The increasing prevalence of diabetes mellitus and the associated high cardiovascular risk has made the non-invasive identification of silent coronary heart disease in diabetic individuals an important issue. This strategy could identify higher risk asymptomatic patients with diabetes mellitus in whom coronary revascularization may improve the outcome beyond that achieved by currently recommended medical management. Stress myocardial perfusion imaging has been shown to be effective in detecting coronary heart disease and predicting adverse cardiac events in asymptomatic diabetic patients. However, the clinical utility of myocardial perfusion scintigraphy is debated intensively due to the paucity of prospective and outcome based evidence. The controversy stems from several observational studies, epidemiologic data and cost-effectiveness analyses. Thus, although several authors and professional organizations advocate the use of stress imaging for screening higher risk asymptomatic diabetic patients, others are cautious in recommending any kind of stress testing in that population. This review is based on a broad survey of the literature and discusses the potential role of stress myocardial perfusion scintigraphy in screening asymptomatic diabetic subjects for coronary heart disease in the current era and in relation with other non-invasive screening tools.

Inducible ischemia and the risk of recurrent cardiovascular events in outpatients with stable coronary heart disease: the heart and soul study

BACKGROUND

Current guidelines do not recommend routine cardiac stress testing in patients with stable coronary heart disease (CHD) unless they report symptoms of angina. Our objective was to compare the prognosis of self-reported angina symptoms, inducible ischemia, or both in patients with stable CHD.

METHODS

We measured self-reported angina by questionnaire and inducible ischemia using treadmill stress echocardiography in 937 outpatients with stable CHD. We used Cox proportional hazard models, adjusted for traditional cardiovascular risk factors, to evaluate the independent association of angina and inducible ischemia with CHD events (myocardial infarction or CHD death) during a mean of 3.9 years of follow-up.

RESULTS

Of the study participants, 129 (14%) had angina alone, 188 (20%) had inducible ischemia alone, and 40 (4%) had both angina and ischemia. Recurrent CHD events occurred in 7% of participants without angina or inducible ischemia, 10% of those with angina alone, 21% of those with inducible ischemia alone, and 23% of those with both angina and inducible ischemia (P < .001). The presence of angina alone was not associated with recurrent CHD events (adjusted hazard ratio, 1.4; 95% confidence interval, 0.7-2.9) (P = .31). However, the presence of inducible ischemia without self-reported angina strongly predicted recurrent CHD events (adjusted hazard ratio, 2.2; 95% CI, 1.4-3.5) (P = .005).

CONCLUSIONS

We found that 24% of patients with stable CHD had inducible ischemia, and more than 80% of these patients did not report angina. The presence of inducible ischemia without self-reported angina is associated with a greater than 2-fold increased rate of recurrent CHD events.

Prevalence of symptomatic and silent stress-induced perfusion defects in diabetic patients with suspected coronary artery disease referred for myocardial perfusion scintigraphy

PURPOSE

Silent myocardial ischaemia--as evaluated by stress-induced perfusion defects on myocardial perfusion scintigraphy (MPS) in patients without a history of chest pain--is frequent in diabetes and is associated with increased rates of cardiovascular events. Its prevalence has been determined in asymptomatic diabetic patients, but remains largely unknown in diabetic patients with suspected coronary artery disease (CAD) in the clinical setting. In this study we therefore sought (a) to determine the prevalence of symptomatic and silent perfusion defects in diabetic patients with suspected CAD and (b) to characterise the eventual predictors of abnormal perfusion.

METHODS

The patient population comprised 133 consecutive diabetic patients with suspected CAD who had been referred for MPS. Studies were performed with exercise (41%) or pharmacological stress testing (1-day protocol, (99m)Tc-sestamibi, 201Tl or both). We used semi-quantitative analysis (20-segment polar maps) to derive the summed stress score (SSS) and the summed difference score (SDS).

RESULTS

Abnormal MPS (SSS> or =4) was observed in 49 (37%) patients (SSS=4.9+/-8.4, SDS=2.4+/-4.7), reversible perfusion defects (SDS> or =2) in 40 (30%) patients [SSS=13.3+/-10.9; SDS=8.0+/-5.6; 20% moderate to severe (SDS>4), 7% multivessel] and fixed defects in 21 (16%) patients. Results were comparable between patients with and patients without a history of chest pain. Of 75 patients without a history of chest pain, 23 (31%, 95% CI=21-42%) presented reversible defects (SSS=13.9+/-11.3; SDS=7.4+/-1.2), indicative of silent ischaemia. Reversible defects were associated with inducible ST segment depression during MPS stress [odds ratio (OR)=3.2, p<0.01). Fixed defects were associated with erectile dysfunction in males (OR=3.7, p=0.02) and lower aspirin use (OR=0.25, p=0.02).

CONCLUSION

Silent stress-induced perfusion defects occurred in 31% of the patients, a rate similar to that in patients with a history of chest pain. MPS could identify these patients with a potentially increased risk of cardiovascular events.

Long-term outcome of patients with silent versus symptomatic ischemia six months after percutaneous coronary intervention and stenting

OBJECTIVES

We sought to evaluate the incidence of silent ischemia versus symptomatic ischemia six months after percutaneous coronary intervention (PCI) and its impact on prognosis and to test the utility of myocardial perfusion single-photon emission computed tomography (SPECT), or MPS, for risk stratification in these patients.

BACKGROUND

Silent ischemia is frequent after PCI. However, little is known about silent ischemia and long-term outcome after PCI and stenting.

METHODS

In 356 consecutive patients with successful PCI and stenting and follow-up MPS after six months, long-term follow-up (4.1 +/- 0.3 years) was performed. The MPS images were interpreted by defining summed stress, rest, and difference scores (summed difference score [SDS] = extent of ischemia) and related to symptoms and outcome. Critical events included cardiac death, myocardial infarction, and target vessel revascularization.

RESULTS

Eighty-one patients (23%) had evidence of target vessel ischemia, which was silent in 62%. The only independent predictor of silent ischemia was SDS (odds ratio 0.64, p = 0.001). During follow-up, 67 critical events occurred. For patients with an SDS of 0, 1-4, and >4, the critical event rates were 17%, 29%, and 69%, respectively. Similarly, patients without ischemia, silent ischemia, and symptomatic ischemia had 17%, 32%, and 52% of critical events, respectively. Diabetes (relative risk 1.98, p = 0.03) and SDS (relative risk 1.2, p < 0.001) were independent predictors of critical events. The MPS image added incremental information for the prediction of critical events.

CONCLUSIONS

Six months after PCI and stenting, 23% of patients had target vessel ischemia, which was silent in 62%. Silent ischemia predicted a worse outcome than did no ischemia and tended to have a better outcome than symptomatic ischemia. This was closely related to the extent of ischemia. The SDS added incremental value to pre-scan findings with respect to diagnosis and prognosis, indicating the utility of MPS for risk stratification after PCI and stenting.

Comparison of late outcome in patients with versus without angina pectoris having reversible perfusion abnormalities during dobutamine stress technetium-99m sestamibi single-photon emission computed tomography

The aim of this study was to assess the prognostic significance of reversible perfusion abnormalities in patients without angina during dobutamine stress technetium-99m sestamibi single-photon emission computed tomography (SPECT). The study comprised 224 patients (age 60 +/- 11 years, 144 men) with completely or partially reversible perfusion abnormalities during dobutamine stress sestamibi SPECT. Follow-up end points were hard cardiac events (cardiac death and nonfatal myocardial infarction). Angina occurred in 93 patients (42%) during the dobutamine stress test (symptomatic ischemia group). The 131 patients without dobutamine-induced angina represented the silent ischemia group. There was no significant difference between patients with and without angina with regard to summed stress perfusion score (5.3 +/- 2.5 vs 5.2 +/- 2.2, p = 0.9) or summed ischemic score (3.1 +/- 1.7 vs 3.2 +/- 1.4, p = 0.7). During a median follow-up of 7.2 years, cardiac death occurred in 14 patients (15%) with and in 21 patients (16%) without angina. Nonfatal myocardial infarction occurred in 8 patients (9%) with and in 13 patients (10%) without angina. In a multivariate analysis model of clinical and perfusion data, independent predictors of cardiac events were age (hazard ratio 1.02, confidence intervals [CI] 1.01 to 1.05 per year increment), diabetes mellitus (hazard ratio 1.9, CI 1.2 to 3.4), and ischemic perfusion score (hazard ratio 2.1, CI 1.3 to 3.8). Patients with silent ischemia defined as reversible perfusion abnormalities without associated angina during dobutamine stress sestamibi SPECT imaging had similar incidences of ischemia and similar cardiac event rates compared with patients with symptomatic ischemia. Therefore, the absence of angina in association with reversible perfusion abnormalities should not be interpreted as a sign of a more benign prognosis.

Prognosis of "clandestine" myocardial ischemia, silent myocardial ischemia, and angina pectoris in medically treated patients

The aim of this study was to assess the prognosis of medically treated patients with "clandestine" myocardial ischemia (perfusion defect without angina and no ST depression > 1 mm during exercise test) compared to those with silent myocardial ischemia (ST-segment depression > 1 mm, without angina) and those with angina pectoris. One hundred twelve patients without previous myocardial infarction were included. All patients underwent a symptom-limited exercise test on a bicycle ergometer, myocardial perfusion technetium-99m-methoxy-isobutyl-isonitrile single-photon emission computed tomography (SPECT), and coronary angiography. They were classified into 3 groups (angina group, 34 patients; silent group, 20 patients; and the clandestine group, 58 patients). The mean follow-up was 3.6 years (range 6 months to 5.5 years). Patients with clandestine ischemia had a lower scintigraphic and angiographic score than patients with silent ischemia (25+/-8 vs 31+/-9 and 24+/-8 vs 29+/-7, p = 0.008, respectively), but the prognosis was similar. Only angina and severe reversible SPECT defects were predictive for cardiac events: death + myocardial infarction + revascularization. We conclude that in medically treated patients without previous myocardial infarction, angina and severe reversible SPECT defects are predictive for cardiac events only when the need for revascularization is included as a cardiac event.