Effects of reduced preload on diastolic filling in essential hypertensive patients with increased left ventricular mass

Beneficial effects of elevating cardiac preload on left-ventricular diastolic function and volume during heat stress: implications toward tolerance during a hemorrhagic insult

Volume loading normalizes tolerance to a simulated hemorrhagic challenge in heat-stressed individuals, relative to when these individuals are thermoneutral. The mechanism(s) by which this occurs is unknown. This project tested two unique hypotheses; that is, the elevation of central blood volume via volume loading while heat stressed would 1) increase indices of left ventricular diastolic function, and 2) preserve left ventricular end-diastolic volume (LVEDV) during a subsequent simulated hemorrhagic challenge induced by lower-body negative pressure (LBNP). Indices of left ventricular diastolic function were evaluated in nine subjects during the following conditions: thermoneutral, heat stress, and heat stress after acute volume loading sufficient to return ventricular filling pressures toward thermoneutral levels. LVEDV was also measured in these subjects during the aforementioned conditions prior to and during a simulated hemorrhagic challenge. Heat stress did not change indices of diastolic function. Subsequent volume infusion elevated indices of diastolic function, specifically early diastolic mitral annular tissue velocity (E') and early diastolic propagation velocity (E) relative to both thermoneutral and heat stress conditions (P < 0.05 for both). Heat stress reduced LVEDV (P < 0.05), while volume infusion returned LVEDV to thermoneutral levels. The reduction in LVEDV to LBNP was similar between thermoneutral and heat stress conditions, whereas the reduction after volume infusion was attenuated relative to both conditions (P < 0.05). Absolute LVEDV during LBNP after volume loading was appreciably greater relative to the same level of LBNP during heat stress alone. Thus, rapid volume infusion during heat stress increased indices of left ventricular diastolic function and attenuated the reduction in LVEDV during LBNP, both of which may serve as mechanisms by which volume loading improves tolerance to a combined hyperthermic and hemorrhagic challenge.

Cardiac systolic and diastolic function during whole body heat stress

During a whole body heat stress, stroke volume is either maintained or slightly elevated despite reduced ventricular filling pressures and central blood volume, suggestive of improved cardiac diastolic and/or systolic function. Heat stress improves cardiac systolic and diastolic function in patients with congestive heart failure, although it remains unknown whether similar responses occur in healthy individuals, which is the hypothesis to be tested. Nine male volunteers underwent a whole body heat stress. Echocardiographic indexes of diastolic and systolic function were performed following a supine resting period, and again following an increase in internal temperature of approximately 1.0 degrees C via passive heat stress. Despite previous reports of heat stress-induced decreases in ventricular filling pressures and central blood volume, no changes in indexes of diastolic function were identified during heating [i.e., unchanged early diastolic mitral annular tissue velocity (E'), mitral inflow during the early diastolic phase (E), the E/E' ratio, and isovolumetric relaxation time]. Heat stress increased late diastolic septal (P = 0.03) and lateral (P = 0.01) mitral annular tissue velocities (A'), mitral inflow velocity during atrial contraction (P < 0.001), and the relative contribution of atrial contraction to left ventricular filling during diastole (P = 0.01), all indicative of improved atrial systolic function. Furthermore, indexes of ventricular systolic function were increased by heat stress [i.e., increased septal (P = 0.001) and lateral (P = 0.01) mitral annular systolic velocities and isovolumic acceleration at the septal (P = 0.03) and lateral (P < 0.001) mitral annulus]. These data are suggestive of improved atrial and ventricular systolic function by the heat stress. Together these data support previous findings, which used the less precise measure of ejection fraction, that heat stress improves indexes of systolic function, while diastolic function is maintained.

Perioperative hypertension: new strategies for management

Perioperative hypertension is a very frequent occurrence and requires the anaesthetist to make clinical decisions regarding antihypertensive therapy, evaluation of risk, cancellation of surgery and treatment of high and low blood pressure. Perioperative management of hypertensive patients must take into account the possible consequences of left ventricular diastolic dysfunction and reduced coronary reserve.

The 'TEI-index' is preload dependent and can be measured by transoesophageal echocardiography during mechanical ventilation

BACKGROUND AND OBJECTIVE

The Doppler-derived echocardiographic TEI-index, defined as the sum of the left ventricular isovolumic contraction and isovolumic relaxation times divided by ejection time, quantifies combined systolic and diastolic ventricular functions. The index has been proposed to be independent of arterial pressure and heart rate, implying a broad clinical usefulness. However, it is unclear whether the index is preload independent. We assessed whether and to what degree the TEI-index is altered by left ventricular loading conditions, and the feasibility of measurement by transoesophageal echocardiography during anaesthesia and mechanical ventilation.

METHODS

We studied 17 anaesthetized mechanically ventilated patients with coronary artery disease during variations in left ventricular preload evoked by head-up and head-down tilt, respectively.

RESULTS

A head-down tilt increasing left ventricular end-diastolic area from 18.8 +/- 4 to 23.7 +/- 4 cm2 (P < 0.05) significantly decreased the TEI-index from 0.5 +/- 0.17 to 0.33 +/- 0.15 (P < 0.05). In contrast, the TEI-index remained unchanged with decreased left ventricular preload (14.4 +/- 3.7 cm2) during head-up tilt.

CONCLUSIONS

An increase in preload decreases the TEI-index indicating its sensitivity to acute increases in left ventricular preload. The TEI-index can be measured perioperatively by transoesophageal echocardiography.

Effect of the Valsalva manoeuver on diastolic filling indices in patients with essential hypertension

In some hypertensive patients, echocardiographic examination does not reveal any pathologic finding in spite of a documented blood pressure elevation. In our study, we investigated the effect of preload reduction with Valsalva manoeuver on transmitral flow velocities in hypertensive patients with normal mitral flow pattern and compared the results with a healthy control group. Sixty-eight patients without evidence of coronary artery disease or heart failure (28 female, 40 male, age 50 +/- 7) were divided in two groups according to their E/A ratio as those with diastolic dysfunction (n = 36) and without diastolic dysfunction (DD(-): n = 32). DD(-) patients and the control group (n = 20) performed Valsalva manoeuver and their pulsed-Doppler mitral flow measurements were repeated at the strain phase. During Valsalva manoeuver, E wave velocity decreased in all subjects. In the controls, peak A velocity showed a similar decline and E/A ratio remained over 1.0. However, in 72% of DD(-) patients A velocity did not change or increased and their E/A ratio fell below 1.0. In 47% of the patients with an E/A ratio reversal after Valsalva manoeuver, myocardial perfusion scintigraphy revealed reversible defects whereas none of the patients whose E/A ratio remained over 1.0 had perfusion defects. It is concluded that: (1) in hypertensive patients with normal E/A ratio Valsalva manoeuver should be performed in order to unmask a probable false normal finding, (2) an important percent of hypertensive individuals have left ventricular relaxation abnormalities, and (3) diastolic dysfunction develops together with a decrease in coronary reserve.