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Dynamic changes in left ventricular outflow tract flow velocities after amyl nitrite inhalation in hypertrophic
S Hadjimiltiades1, I P Panidis, M McAllister
1Likoff Cardiovascular Institute, Hahnemann University Hospital, Philadelphia, PA.
Insights
Doppler echocardiography effectively assesses left ventricular outflow tract (LVOT) velocity and pressure gradients in hypertrophic cardiomyopathy (HC). Amyl nitrite provocation significantly increases these values in HC patients, independent of medication.
Area of Science:
- Cardiology
- Medical Imaging
- Physiology
Background:
- Hypertrophic cardiomyopathy (HC) is a complex cardiac condition.
- Assessing left ventricular outflow tract (LVOT) obstruction is crucial for managing HC.
- Doppler echocardiography offers non-invasive hemodynamic assessment.
Purpose of the Study:
- To evaluate the utility of Doppler echocardiography in measuring LVOT peak velocity and pressure gradients in patients with HC.
- To assess the effect of amyl nitrite inhalation on LVOT hemodynamics in HC.
- To differentiate HC patients from those with other forms of left ventricular hypertrophy.
Main Methods:
- Doppler echocardiography was used to record LVOT peak velocity at rest and after amyl nitrite inhalation in patients with HC, healthy controls, and hypertensive individuals.
- The modified Bernoulli equation calculated the LVOT pressure gradient.
- Continuous wave Doppler technique was employed for velocity measurements.
Main Results:
- Amyl nitrite inhalation caused significant increases in heart rate and decreased systolic blood pressure across all groups.
- Both peak LVOT velocity and pressure gradient increased significantly after provocation in all patients.
- The increase was markedly more pronounced in HC patients, with characteristic late systolic peak velocity patterns observed.
Conclusions:
- Doppler echocardiography is a reliable method for assessing LVOT velocity and pressure gradients in HC, both at rest and after provocation.
- Amyl nitrite-induced dynamic changes in LVOT velocity are characteristic of obstructive HC.
- The observed hemodynamic changes appear independent of beta-blocker or calcium channel blocker therapy in the tested dosages.
Abstract:
Doppler echocardiography was performed in 21 patients with hypertrophic cardiomyopathy (HC), in nine patients with no evidence of left ventricular (LV) hypertrophy by two-dimensional echocardiography, and in five patients with systemic hypertension and concentric LV hypertrophy. The LV outflow tract (LVOT) peak velocity was recorded by continuous wave Doppler technique at rest and after amyl nitrite inhalation. The LVOT pressure gradient was calculated by the modified Bernoulli equation. A significant increase in heart rate and a drop in systolic blood pressure were observed in all patients after amyl nitrite inhalation; no adverse effects were encountered. The peak LVOT velocity and pressure gradient increased significantly after provocation in all patients, but the increase was much more pronounced in patients with HC (peak LVOT velocity increased from 2.2 +/- 0.8 to 4.3 +/- 1.0 m/sec and peak gradient increased from 22 +/- 17 to 78 +/- 36 mm Hg). The Doppler spectral signal in patients with HC demonstrated a characteristic contour, with peak velocity occurring in late systole. However, the observed increase in LVOT peak velocity was not statistically different between treated (with beta-blockers and calcium blockers) and untreated patients with HC. We conclude that LVOT peak velocity and pressure gradients in patients with HC can be readily assessed by Doppler echocardiography both at rest and after amyl nitrite inhalation. The dynamic changes in LVOT velocity induced by this provocation have certain characteristic features in obstructive HC but appear to be independent of the medical regimen used, at least in the dosages tested in our study.