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Abstract & Commentary
Synopsis: Reflex tachycardia, during a Valsalva maneuver, is a sign of normal LV filling.
Source: Marrill CA, et al. J Am Soc Echocardiogr. 2004;17:634-637.
Despite the overall usefulness of mitral Doppler flow velocity profiles for estimating diastolic function of the left ventricle, differentiating normal from pseudo-normal filling patterns is difficult. The response to a Valsalva maneuver has been suggested to be of help in this differentiation, but in some patients, the Valsalva induced tachycardia fuses the mitral E and A velocities, rendering analysis impossible. Marrill and colleagues from the Mayo Clinic hypothesized that tachycardia induced by a Valsalva maneuver may be of diastolic value in and of itself. Thus, they studied 77 patients referred for left heart catheterization. During catheterization, left ventricular pre A-wave pressure in diastole was recorded, as was the heart rate and aortic pressure during Valsava maneuver. The baseline ECG R-R interval, divided by the shortest R-R interval during the Valsalva maneuver, was the R-R ratio.
Results: A pre A-wave LV diastolic pressure of 18 mm Hg was chosen as the cut point; 58 patients had pressures < 18, and 19 had higher pressures. An R-R ratio of > 1.1 had a positive predictive value of 94% for a pre A-wave pressure < 18. In patient subgroups with LV ejection fraction above or below .50, age above or below 60, and presence or absence of beta blocker therapy, the results were not significantly different. In diabetics, the positive predictive value dropped to 75%, but there were only 4 patients in this group. Marrill et al concluded that reflex tachycardia, during a Valsalva maneuver, is a sign of normal LV filling.
Comment by Michael H. Crawford, MD
Differentiating normal from pseudo-normal mitral Doppler flow velocity patterns can be aided by a Valsalva maneuver. The Valsalva maneuver transiently reduces LV filling by increasing intra-thoracic pressure during the strain phase. In normals, reduced LV filling results in diminution of both the E- and A-waves of mitral inflow velocity equally. However, in some normals, the resulting reduced stroke volume leads to reflex tachycardia and fusion of the E- and A-waves. This study shows that the increase in heart rate itself is a sign of normal filling pressures. In patients with high filling pressures, the reduced filling volume during Valsalva decreases the E-wave, but accentuates the A-wave, revealing the abnormal filling pattern. Since many patients with high filling pressures are on a flat starling curve, the reduced filling changes stroke volume very little, so no reflex tachycardia is seen. However, an abnormal Valsalva response can be due to confounders such as older age, beta blockers, and autonomic dysfunction (diabetes). Thus, an abnormal Valsalva response is of less diagnostic value than a normal one, but in the former case, the E- and A-wave characteristics can be interpreted. One caveat is that the heart rate response must be continuously assessed so the fastest rate is detected, usually during the strain or just after. Later, the increased stroke volume, post release of the strain, results in a bradycardia in normals. Another is that a falsely abnormal test can be seen with inadequate strain. The adequacy of the strain can be assessed by a mouth pressure gauge or by feeling the abdominal muscles contract.
Dr. Crawford, Professor of Medicine, Associate Chief of Cardiology for Clinical Programs University of California San Francisco, is Editor of Clinical Cardiology Alert.