Abstract & Commentary
With Comments by Michael H. Crawford, MD, Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco, Editor, Clinical Cardiology Alert.
Synopsis: The observed age-related changes in mitral Doppler filling velocity characteristics are not due to differences in left atrial pressure over the physiologic range of pressures.
Source: Prasad A, et al. Circulation. 2005;111:1499-1503.
Doppler diastolic mitral valve flow velocity alterations in older individuals is thought to be due to age-related impaired left ventricular (LV) relaxation and associated increases in left ventricular end diastolic pressure. However, other Doppler measurements, such as pulmonary vein flow velocity, do not support increases in left atrial pressure in normal healthy elderly subjects. Thus, this study sought to clarify this issue by measuring pulmonary capillary wedge pressure (PCWP) and Doppler indices at different loading conditions in 12 healthy elderly subjects (mean age 69 years) and 12 healthy young controls (mean age 35 years) who had similar activity levels, resting blood pressure, and heart rate. A balloon-tipped fluid-filled catheter was used for obtaining PCWP. Loading conditions were varied by lower body negative pressure (decrease) and warm isotonic saline (increase). Catheter frequency response was measured and found to be adequate. Doppler recordings were done immediately after the catheter measures because the patients required turning to the left lateral position. PCWP was measured at 6 points throughout the cardiac cycle. Mitral Doppler measures included the peak E and A velocities and the isovolumic relaxation time (IVRT).
Results: E/A was 0.8 in the seniors vs 1.7 in the controls (P < .001). IVRT was 147 ms in the seniors vs 108 ms in the controls (P < .001). The PCWP was slightly higher at all 6 measurement points vs the controls (average difference about 1.0 mmHg) during negative pressure, which was not statistically significant. During saline infusion, the waveforms were almost identical. Prasad and colleagues concluded that the observed age-related changes in mitral Doppler filling velocity characteristics are not due to differences in left atrial pressure over the physiologic range of pressures.
Comments
This study is of interest because it helps clarify the observed aging related changes in mitral Doppler filling velocity. The study is robust because care was taken to use a catheter system with an adequate frequency response. The frequency response was 8 Hz, and an end-hole catheter across a patent foramen ovale in one subject showed that left atrial pressure waves forms were < 4 Hz. Also, multiple pressure points were measured throughout the cardiac cycle rather than just mean pressure. In addition, the filling pressure was raised and lowered to be sure the PCWP values reflected the physiologic range of pressures. Finally, the elderly subjects were carefully evaluated to be sure they were free of cardiac disease. This careful study showed no difference in left atrial pressure that would explain the Doppler findings.
The Doppler mitral velocities represent the pressure difference between the LA and LV. Since LA pressure is not different between seniors and young controls, LV pressures must be different during diastole. LV pressures were not directly measured in this study but, by inference, early LV diastolic pressure must be higher since the E wave velocity was lower. This agrees with animal data suggesting that early active LV relaxation is impaired in older animals. Also, late diastolic LV pressures must be lower since the A wave velocity was higher. The origin of this inference is unclear since other studies have shown reduced passive compliance of the LV, which would be expected to increase LV filling pressure in late diastole. Clearly, more work needs to be done on this issue, but for now the practical message is that it should not be assumed that LA pressure is elevated in patients with mitral Doppler evidence of impaired relaxation unless other findings suggest increased LA pressure such as pulmonary vein flow characteristics, tissue Doppler E/E´ or LA enlargement.
The observed age-related changes in mitral Doppler filling velocity characteristics are not due to differences in left atrial pressure over the physiologic range of pressures.
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