Noninvasive analysis of ventricular diastolic performance: in quest of a clinical tool

Ventricular function

Multiple modalities contribute to the evaluation of ventricular function. The role of cineangiography, echocardiography, MR imaging, ultrafast CT, and nuclear medicine continue to evolve and improve our understanding of the physiology and pathophysiology of ventricular function. This article discusses the use and limitation of each modality.

Increased circulating atrial natriuretic factor concentrations in patients with chronic heart failure after inhibition of neutral endopeptidase: effects on diastolic function

OBJECTIVE

+/- Candoxatrilat was used to raise atrial natriuretic factor (ANF) concentrations in patients with heart failure, and the effects on left ventricular systolic and diastolic function were studied to determine the contribution of peripheral and central mechanisms to the haemodynamic effects.

DESIGN

This was a single blind, randomised comparison of +/- candoxatrilat and placebo in patients with mild heart failure. All patients received two intravenous doses of +/- candoxatrilat and two placebo doses on four consecutive days.

SETTING

A teaching hospital department of cardiology.

PATIENTS

Six men (mean age 52 years) with mild heart failure (New York Heart Association class II) due to ischaemic heart disease (four patients) or dilated cardiomyopathy (two patients) were included. Mean ejection fraction was 37.5% and mean peak oxygen consumption was 20.4 ml/min/kg.

MAIN OUTCOME MEASURES

Plasma ANF concentrations, haemodynamic indices and left ventricular diastolic function measured by early to atrial filling rate (E:A ratio) with Doppler echocardiography were determined before and after +/- candoxatrilat and placebo.

RESULTS

+/- Candoxatrilat caused a threefold rise of plasma ANF compared with placebo (p < 0.005), but there was no significant change in heart rate, blood pressure, or cardiac output. Mean right atrial pressure fell from 6.7 to 4.7 mmHg (NS) and pulmonary artery wedge pressure fell from 9.2 to 6.7 mmHg (p < 0.05). Doppler echocardiographic measurements of transmitral blood flow showed a significant fall in peak early left ventricular filling velocity from 39.5 to 34.2 cm/s (p < 0.05), along with a non-significant rise in peak atrial filling velocity from 39.7-41.6 cm/s after +/- candoxatrilat. The E:A ratio, a Doppler index of left ventricular diastolic function, fell from a mean of 1.04 to 0.87 (p < 0.05).

CONCLUSIONS

+/- Candoxatrilat increased plasma ANF concentrations and reduced right atrial and pulmonary artery wedge pressures. No evidence of an improvement in left ventricular systolic or diastolic function was found, so the fall in preload was due to peripheral effects, either an increase in venous capacitance or a fall in circulating blood volume.

The role of Doppler echocardiography in the assessment of left ventricular diastolic function

The role of Doppler echocardiography of transmitral filling velocities in the assessment of diastolic function in man has not been adequately defined. It is now appreciated that multiple interacting factors such as loading conditions influence the transmitral velocity profile independent of intrinsic left ventricular diastolic function. Extrapolating the status of diastolic function from the transmitral velocity profile is complicated by these factors. The load dependence of ventricular filling has tempered the initial enthusiasm for the clinical application of the Doppler technique. In the present review, studies examining invasive parameters of diastolic function and Doppler indices of diastolic filling are discussed to gain greater insight and understanding of the role of Doppler echocardiography in the noninvasive assessment of diastolic function. These studies have demonstrated a relatively consistent influence of left ventricular relaxation, chamber stiffness, and left atrial pressure on the transmitral velocity filling profile. Impairment of relaxation impedes early filling and may result in a compensatory increase in atrial contribution to filling. An independent decrease in left atrial pressure from altered loading conditions may also reduce filling in early diastole. Increased left ventricular chamber stiffness (i.e., noncompliant left ventricle) impairs atrial contribution to filling and may enhance early filling. Theoretically, reduced left atrial contractility may decrease atrial contribution to filling. Pulmonic vein flow demonstrating increased retrograde flow during atrial systole helps to exclude impaired left atrial contractility. An increased left atrial pressure from altered loading conditions may also augment early filling. Therefore, an invasive or clinical assessment of left atrial pressure as being increased, decreased, or normal greatly aids in the interpretation of the transmitral filling velocity profile when inferences on the status of diastolic function are being made. Diastolic dysfunction is likely when a given pattern of filling cannot be explained on the basis of left atrial pressure. In situations where reasonable estimates on the status of left atrial pressure cannot be done, striking alterations in the transmitral velocity filling profile may be useful.

Exercise intolerance in patients with heart failure and preserved left ventricular systolic function: failure of the Frank-Starling mechanism

Invasive cardiopulmonary exercise testing was performed in 7 patients who presented with congestive heart failure, normal left ventricular ejection fraction and no significant coronary or valvular heart disease and in 10 age-matched normal subjects. Compared with the normal subjects, patients demonstrates severe exercise intolerance with a 48% reduction in peak oxygen consumption (11.6 +/- 4.0 versus 22.7 +/- 6.1 ml/kg per min; p less than 0.001), primarily due to a 41% reduction in peak cardiac index (4.2 +/- 1.4 versus 7.1 +/- 1.1 liters/min per m2; p less than 0.001). In patients compared with normal subjects, peak left ventricular stroke volume index (34 +/- 9 versus 46 +/- 7 ml/min per m2; p less than 0.01) and end-diastolic volume index (56 +/- 14 versus 68 +/- 12 ml/min per m2; p less than 0.08) were reduced, whereas peak ejection fraction and end-systolic volume index were not different. In patients, the change in end-diastolic volume index during exercise correlated strongly with the change in stroke volume index (r = 0.97; p less than 0.0001) and cardiac index (r = 0.80; p less than 0.03). Pulmonary wedge pressure was markedly increased at peak exercise in patients compared with normal subjects (25.7 +/- 9.1 versus 7.1 +/- 4.4 mm Hg; p less than 0.0001). Patients demonstrated a shift of the left ventricular end-diastolic pressure-volume relation upward and to the left at rest. Increases in left ventricular filling pressure during exercise were not accompanied by increases in end-diastolic volume, indicating a limitation to left ventricular filling.(ABSTRACT TRUNCATED AT 250 WORDS)

Imaging congenital heart disease

When defined in a broad sense, imaging is the most important aspect of modern pediatric cardiovascular medicine. Definition of anatomic defects is now accurately and easily obtained with physical inspection, x-ray technology (including roentgenology, fluoroscopy, and cineangiography), and echocardiography. Echocardiography, with the addition of Doppler and color flow Doppler, is the most important development in clinical cardiac imaging in the past decade. The exciting new areas of "imaging" are in cardiac functional analysis and metabolic evaluation. Viewing the heart at the cellular or biochemical level is the challenge of the future. The new technology offered by computed tomography, positron emission tomography, and nuclear magnetic resonance imaging begins to provide the ability to image the domain of cellular and biochemical function.