Left Atrial Pressure Estimation by Echo Doppler in Heart Failure Patients
Abstract & Commentary
By Michael H. Crawford, MD, Editor
Sources: Ritzema JL, et al. Serial doppler echocardiography and tissue doppler imaging in the detection of elevated directly measured left atrial pressure in ambulant subjects with chronic heart failure. JACC Cardiovasc Imaging 2011;4:927-934. Nagueh SF. Noninvasive estimation of LV filling pressures in heart failure and reduced ejection fraction: Revisited and verified. JACC Cardiovasc Imaging 2011;4:935-937.
The management of chronic heart failure patients would benefit from an accurate noninvasive way to estimate left atrial pressure (LAP). This study from New Zealand sought to determine the accuracy of Doppler echocardiography for this purpose. They studied 15 chronic outpatient heart failure patients who had a permanently implanted direct LAP measuring device (Heart POD, St. Jude Medical) by serial Doppler echo studies and compared several measures of diastolic function to the LAP. The 15 patients had 60 simultaneous echo and LAP measurements with a median of four per patient over 1 year. Patients with atrial fibrillation, stenotic valve disease, hypertrophic cardiomyopathy, moderate or more semilunar valve regurgitation, valve prostheses, or significant pericardial effusion were excluded. Baseline mean LAP was 17 mmHg and mean ejection fraction by echo was 32%. There was a large range of LAP measurements (5 to 39 mmHg). An LAP > 15 mmHg was seen in 52% and in 35% it was > 20 mmHg. Reliable tissue Doppler studies were obtained in > 80% and pulmonary venous flow was acquired in > 70%. The ratio of mitral E velocity to tissue Doppler mitral annular velocity (E/e'), averaging the medial and lateral early annular velocities (e'), was the best predictor of LAP > 15 mmHg: sensitivity 84, specificity 96, positive-predictive valve 95, negative predictive value 85, and accuracy 90. The average and the medial value were better than the lateral value for (e'). An average E/e' value of > 14, medial > 15, or a lateral of > 12 had the best receiver operating curves. All three measures were superior to all the other echo Doppler parameters evaluated, with an area under the receiver operating curve of > 0.90. The authors concluded that the E/e' ratio can reliably predict LAP in chronic heart failure patients over time.
Commentary
There has been considerable controversy regarding the use of left ventricular (LV) filling parameters to estimate LAP. Early studies based in the cardiac catheterization laboratory established a close relation between E/e' and mean LAP (pulmonary capillary wedge pressure) but less so with LV end diastolic pressure. Whether it would be accurate over time in ambulatory patients with various medication changes, progressive disease, and devices such as resynchronization was addressed by this study. They found the best accuracy with an average of the medial and lateral annular tissue Doppler velocities for determining e', but the medial velocity performed almost as well. A medial E/e' > 15 was associated with LAP > 15 mmHg (88% accuracy vs 90% by the average). With medial E/e' >18, LAP > 15 mmHg was almost certain and an E/e' < 12 essentially ruled out a LAP > 15 mmHg. The detection of a LAP > 20 mmHg was less robust with an accuracy of 79% for the medial E/e' > 15. The higher the LAP the less linear was the association with E/e'; perhaps because most patients with LAP > 25 mmHg had moderate mitral regurgitation which tends to elevate E out of proportion to any reduction in e'. The measurement of E/e' was also highly reproducible; intraobserver variability for E was 4% and e' 7%. Thus, E/e' should be an accurate method for detecting when patients have LAPs in the decompensated range.
Of course there are some pitfalls to this measurement. Not all patients will have technically adequate studies to make these measurements. For example, patients with rapid heart rates will have fusion of the mitral E and A velocities and significant mitral regurgitation will influence the E velocity as discussed above. Also, tissue Doppler velocity is not as reliable for assessing LAP in normals, patients with mitral valve disease, LBBB, paced rhythms, and constrictive pericarditis. In addition, there are few data in patients with hypertrophic cardiomyopathy and pericardial effusion. With these caveats in mind, Doppler echo measurements of E/e' should be a useful estimate of LAP in acute and chronic heart failure patients, no matter how they are treated.
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