Myocardial contraction fraction: a volumetric index of myocardial shortening by freehand three-dimensional echocardiography.

OBJECTIVES

This study sought to evaluate myocardial contraction fraction (MCF) as an index of myocardial shortening by comparison to conventional shortening indices in patients with hypertensive hypertrophy, athletes with physiologic hypertrophy and sedentary normal adult subjects.

BACKGROUND

A significant percentage of patients with hypertensive hypertrophy have "normal" or "preserved" left ventricular (LV) systolic function by conventional echocardiographic measures whereas their systolic function is depressed when measured by the two-dimensional echocardiographic mid-wall shortening fraction (MWSF). A three-dimensional echocardiographic measure of myocardial shortening analogous to MWSF has been lacking. We describe a volumetric measure of myocardial shortening, the MCF, as the ratio of stroke volume (SV) to myocardial volume (MV), and hypothesize that it may be useful to compare myocardial performance in patients with different degrees and types of hypertrophy.

METHODS

We compared the MCF using freehand three-dimensional echocardiographic reconstruction of the LV to conventional measures of LV function (ejection fraction [EF], endocardial shortening fraction [SF] and MWSF) in subjects with pathologic hypertensive hypertrophy, heart failure symptoms and preserved EF (n = 17), athletes with physiologic hypertrophy (n = 41) and normal sedentary adults (n = 80).

RESULTS

The EF was in the normal range for all three groups. The MCF was lower in hypertensive hypertrophy compared with normal subjects (0.33 +/- 0.05 vs. 0.44 +/- 0.07, p < 0.01). It also successfully differentiated physiologic hypertrophy from normal subjects (0.50 +/- 0.05 vs. 0.44 +/- 0.07, p < 0.01). The endocardial SF did not distinguish athletes from normal subjects and the MWSF did not distinguish hypertensive from physiologic hypertrophy.

CONCLUSIONS

The MCF, a volumetric measure of myocardial shortening, demonstrates that myocardial shortening is decreased in hypertensive hypertrophy and increased in physiologic hypertrophy. The MCF may be useful in assessing differences in myocardial performance in patients with similar degrees of hypertrophy.