DYNAMIC INTRAVENTRICULAR OBSTRUCTION DURI NG DOBUTAMINE STRESS ECHOCARDIOGRAPHY - DETERMINANTS OF THE PHENOMENON AND CLINICAL CONSEQUENCES

Dobutamine stress echocardiography (DSE) leads to strong hypercontract ion, tachycardia, and peripheral vasodilatation. In previous studies s ystolic obstruction of the left ventricular outflow tract (LVOT) was o bserved as a result of these factors. To evaluate left ventricular fun ction and morphology in patients (pts) with induced systolic LVOT obst ruction, we used continuous wave (CW) doppler registrations in combina tion with quantitative 2-D-echocardiography in 100 pts during routinel y performed DSE (5-40 mu g/kg/min). In addition left ventricular wall thickness was measured. Symptoms were registrated using a standardised questionaire and cardiac arrhythmias were counted over a two minute i ntervall at rest and during the maximal heart rate of each patient. Du ring DSE dynamic flow acceleration with late systolic peak velocity ab ove 2 m/second (s) was considered to represent LVOT obstruction in pts with normal flow profiles in the LVOT before infusion of dobutamine. For invasive studies pts were investigated with femoral catheterisatio n by the method of Judkins. A greater than 50 % stenosis was judged to be significant. Results: Examinations in 73 pts provided data of suff icient quality for echocardiographic and Dopplersonographic evaluation s. 39 pts, 26 men, 13 women, mean age 64 +/- 8 years, developed late s ystolic flow velocities above 2 m/s and therefore formed the obstructi ve group (grp A). Grp B consisted of 34 pts, 26 men and 8 women, mean age 66 +/- 10 years, who showed normal time velocity integrals during DSE. In 41 pts invasive data provided information concerning the exist ence and severity of coronary artery disease. There were no significan t differences in the increase of heart rate, the product of maximal sy stolic blood pressure and maximal heart rate or the percentage of pts, who reached their age corrected submaximal heart rate during DSE. Obs tructive pts (group A) showed late systolic dynamic acceleration of sy stolic now with a mean maximal speed of 315.4 +/- 139.8 cm/s, which pe aked 0.12 +/- 0.04 s after the R-wave. From the velocities we calculat ed a mean pressure gradient of 47.5 +/- 39.7 mmHg using the modified B ernoulli equation. Group B patients showed lower and earlier maximal s peeds with a mean value of 158.2 +/- 37.6 cm/s, 0.09 +/- 0.04 s after the R-wave, corresponding to a pressure gradient of 10.6 +/- 4.9 mm Hg (p < 0.001). Ejection fractions were higher (p < 0.001) before the te st in grp A: 68.2 +/- 8 % compared to 55.7 +/- 10.4 % in B. This diffe rence increased during peak stress: 74.1 +/- 7.7 % compared to 59.5 +/ - 12.8 %. Enddiastolic (EDVI) and endsystolic volume indexes (ESVI) we re lower in grp A (p < 0.001). During DSE, the decrease in ESVI was so mewhat stronger for pts in grp A. Left ventricular hypertrophy was mor e often seen with obstruction. Septal thickness was increased in A: 1. 45 +/- 0.34 cm compared to 1.13 +/- 0.27 cm in B (p < 0.001). Left ven tricular posterior wall measured 1.03 +/- 0.28 cm in A and 0.83 +/- 0. 23 cm in B (p < 0.01). 27 pts in grp B and only 9 in grp A had a histo ry of previous myocardial infarction. Showing no difference at rest, w all motion score indexes raised under DSE in both groups and developed significantly higher scores in grp B at peak stress: 1.30 (1.0-1.90) compared to 1.18 (1.0-1.75) in A. We observed typical chest pain more often in grp B. Unspecific symptoms and arrhythmogenic complications w ere not statistically different, with the exception of ventricular big eminy which was more often observed in grp B. A decline in the diastol ic blood pressure was observed in pts with very severe obstruction (> 3.5 m/s, p < 0.05). Sensitivity of DSE was 84 %, specificity 79 %. No significant differences between pts with and without obstruction were observed. Summary: Intraventricular obstructions during DSE are often observed in pts with normal systolic function at rest and during peak stress, especially in the case of left ventricular hypertrophy. This f low pattern is not regularly correlated to clinical signs, symptoms or complications. It did not impair diagnostic accuracy concerning the d etection of significant coronary artery disease in our pts.