Echocardiographic Screening of the General Population and Long-Term Survival: A Randomized Clinical Study
Can routine echocardiographic screening in the general population reduce the risk of cardiovascular events or all-cause mortality?
This was a substudy of the Tromsø Study, a population-based, prospective evaluation of adults in Tromsø, Norway. A first visit was attended by 27,159 study subjects, after which all patients 55-74 years old and 5-10% of those ages 25-54 and 75-85 were invited to a second visit for more intensive evaluation. A final study population comprised 6,861 individuals who were randomized to a standard examination during which baseline information regarding cardiovascular risk factors, hypertension, medication, other demographics, as well as physical examination were performed. The second limb of the study involved complete two-dimensional echocardiogram and Doppler for evaluation of cardiac structure and function. Predefined abnormalities on echocardiography for which referral for follow-up clinical examination was indicated included wall thickness >14 mm, aortic root diameter >4.5 cm, mitral stenosis, aortic stenosis (peak >30 mm Hg), significant mitral insufficiency, left ventricular diastolic diameter >6.5 cm, ejection fraction <50%, significant aortic insufficiency, or other anatomic abnormalities. Patients were followed for all-cause mortality, as well as cardiovascular events of myocardial infarction and stroke.
There were 3,272 patients in the echocardiographic screening group and 3,589 in the control group. In the echocardiographic cohort, 362 participants met criteria for referral, 290 of whom were followed by the division of cardiology according to standard clinical practice. The groups were statistically identical with respect to age, gender breakdown, baseline blood pressure, prevalence of smoking, diabetes, prior coronary artery disease, family history of premature myocardial infarction, and medication use. Follow-up examination in the echo screening group identified 290 patients (8.9%) with abnormal findings requiring follow-up. Cardiac pathology identified in the screening group included valvular disease in 108 (3.3%), including biscuspid aortic valve in 2, aortic insufficiency in 42, aortic stenosis in 31, mitral insufficiency in 51, and mitral stenosis in 5. Ventricular hypertrophy was noted in 33 (1%) and ventricular dysfunction in 34 (1%). Over 15 years of follow-up, there were 880 deaths in the screening group (26.9%) and 989 (27.6%) in the control group. Death due to heart disease was noted in 250 and 299 subjects, sudden death in 17 and 19, myocardial infarction in 420 (12.8%) and 484 (13.5%), and stroke in 321 (9.8%) and 343 (9.6%). There were no statistical differences in event rates between the screening and control groups. On subset analysis, there were no statistically significant differences in all-cause mortality in patients with hypertension or diabetes, diabetes, or in three-strata of calculated cardiovascular risk. In an unadjusted model, there was excess mortality in the screening group for patients with a family history of premature coronary artery disease, which was not significant after adjustment for multiple comorbidities.
The authors concluded that routine echocardiographic screening of the general population does not reduce all-cause cardiovascular mortality or stroke.
This long-term longitudinal study nicely demonstrates that screening echocardiography done in a blind fashion without a clear cut indication confers no beneficial impact on overall mortality or rates of cardiovascular events or stroke. A total of 362 subjects had identifiable abnormalities on screening echocardiography, 290 of whom were actively followed by the division of cardiology at the investigating institution. The single most prevalent abnormality to be identified in the screening group was valvular heart disease, including a remarkably low prevalence of bicuspid aortic valve (<1%) and variable degrees of mitral stenosis or insufficiency. Without further information regarding severity, it is difficult to come to conclusions as to whether the valve lesions would be anticipated to result in cardiovascular mortality over the 15-year follow-up. Similarly, other entities such as ventricular hypertrophy (presumably related to hypertension) would be equivalently present in the nonechocardiographic subgroup, as would asymptomatic left ventricular dysfunction, left atrial dilation, and aortic dilation. Without information with respect to the severity of these lesions, and whether they would cross thresholds where therapeutic intervention would be likely to be beneficial, it is difficult to say whether echocardiography plausibly would have impacted outcome. In an era of concern regarding overutilization and occasionally a push for an abbreviated ultrasound exam using a hand-held device, this study nicely demonstrates that major morbidity and mortality are not impacted by such a strategy in the general (presumably asymptomatic) population, and that echocardiography (and other imaging modalities) should be reserved for targeted evaluation of individuals clinically suspected of having specific diseases for which specific therapy is intended.
Keywords: Coronary Artery Disease, Stroke, Myocardial Infarction, Ventricular Dysfunction, Follow-Up Studies, Norway, Mitral Valve Insufficiency, Risk Factors, Prevalence, Cardiology, Mitral Valve Stenosis, Heart Valve Diseases, Hypertension, Diabetes Mellitus, Echocardiography
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