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LV Shape Predicts Different Types of Cardiovascular Events
Study Questions:
Do indices of left ventricular (LV) sphericity predict subsequent cardiovascular events including coronary heart disease (CHD), all cardiovascular disease (CVD), heart failure (HF), and atrial fibrillation (AF)?
Methods:
This is a substudy of the Multiethnic Study of Atherosclerosis (MESA) in which cardiac magnetic resonance imaging (MRI) was performed in 5,004 patients at the time of a baseline examination between calendar year 2000 and 2002. At baseline, all individuals were free of clinically apparent CVD and were followed for a median of 10.2 years for development of endpoints as noted above. Cardiac MRI was analyzed to calculate a sphericity dimension index defined as LV diameter divided by maximum LV length. A sphericity volume index was also calculated from the LV volume. LV sphericity was divided into quintiles. The first quintile was defined as low sphericity and the highest quintile defined as high sphericity with quintiles 2-4 defined as the reference group.
Results:
Comparison of the three patient subgroups revealed equivalent ages in all three, while 58.3% of quintile 1 was male compared to 38.6% of quintile 5. Framingham CVD risk score was highest in quintile 1 and lowest in quintile 5. Coronary heart disease (CHD) was noted in 8.35% of quintile 1 and 5.92% of quintile 5, while all CVD was noted in 11.07% of quintile 1. (For all noted comparisons, p < 0.05 compared to the reference group). High sphericity in diastole conferred an odds ratio of 1.49 for development of HF, which remained statistically significant in a stepwise model including background demographics, concurrent hypertension, ejection fraction, and other variables. Similarly, high sphericity at end-diastole confirmed an odds ratio for incident AF of 1.55, which remained statistically significant after stepwise modeling.
Conclusions:
In a population free of clinically apparent CVD at baseline, low sphericity is a predictor of subsequent CHD, CVD, and HF over a 10-year follow-up, while extreme sphericity is a strong predictor of HF and AF.
Perspective:
This study of over 5,000 patients who were initially free of clinical CVD demonstrates a relationship between LV remodeling and subsequent cardiac events. Both extremes of remodeling were represented in the sphericity groups, with group 1 (low sphericity) having more conical left ventricles. This group probably represents a population with concentric remodeling and hypertrophy, and experienced a higher rate of subsequent recognition of CHD, CVD in general, and HF among initially asymptomatic patients. Presumably in this population, HF was the subset with preserved ventricular function. The quintile with the highest sphericity had a higher rate of incident HF and AF. This is the subset with the more globular LV shape, and although not classified as such, the HF is presumed related to systolic dysfunction. In many, but not all analyses, sphericity was an independent predictor of events after adjusting for multiple demographic features and traditional risk factors. The role that this observation may play in clinical care is uncertain at this time, but certainly ventricular shape and remodeling may allow identification of subsets of patients at greater or lesser risk of developing specific endpoints for whom therapeutic trials may be considered.
Keywords: Atrial Fibrillation, Cardiovascular Diseases, Coronary Artery Disease, Diagnostic Imaging, Diastole, Heart Failure, Hypertension, Hypertrophy, Magnetic Resonance Imaging, Primary Prevention, Risk Factors, Ventricular Remodeling
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