Evaluation of preload reserve during isometric exercise testing in patients with old myocardial infarction: Doppler echocardiographic study

The impact of isometric handgrip testing on left ventricular twist mechanics

Left ventricular (LV) rotation occurs due to contraction of obliquely oriented myocardial fibres. Left ventricular twist (LVT) results from rotation of the apex and base in opposite directions. Although LVT is altered in various cardiac diseases, physiological factors that affect LVT remain incompletely understood. Isometric handgrip testing (IHGT), a well-established laboratory-based technique to increase LV afterload, was performed for 3 min at 40% maximum force generation in healthy human subjects (n = 18, mean age 29.7 ± 2.7 years). Speckle-tracking echocardiography was used to measure LV volumes, LV apical and basal rotation, peak systolic LVT and peak early diastolic untwisting rate (UTR) at rest and at peak IHGT. IHGT led to significant increase in systemic blood pressure (systolic, 120.6 ± 9.7 vs. 155.6 ± 14.5 mmHg, P < 0.001; diastolic, 67.5 ± 6.4 vs. 94.1 ± 21.1 mmHg, P < 0.001) and LV end-systolic volume (44.2 ± 7.8 vs. 50.5 ± 10.8 ml, P = 0.005), as well as a significant increase in heart rate (62.8 ± 11.7 vs. 84.7 ± 13.8 beats min−1; P < 0.001). IHGT produced a significant acute reduction in LV stroke volume (63.9 ± 12.0 vs. 49.4 ± 7.8 ml, P < 0.001). In this setting, there was a significant decrease in peak systolic apical rotation (11.9 ± 3.0 vs. 8.6 ± 2.2 deg, P < 0.001) and a resultant 25% decrease in peak systolic LVT (16.6 ± 2.8 vs. 12.5 ± 2.8 deg, P < 0.001). The magnitude of peak early diastolic UTR did not change (−114.5 ± 26.4 vs. −110.6 ± 39.8 deg s−1, P = 0.71). Peak systolic apical rotation and LVT decrease during IHGT in healthy humans. This impairment of LV twist mechanics may in part underlie the LV dysfunction that can occur in the clinical context of acute increase in afterload.

Non-invasive ultrasonic cardiac output monitoring in exercise testing

BACKGROUND

The purpose of this study was to evaluate the relationship of breath-by-breath oxygen uptake (VO(2)) and CO, cardiac index (CI), stroke volume (SV) and heart rate (HR) determined by a non-invasive continuous wave (CW) Doppler-based system (USCOM) in healthy adolescent and adult athletes during exercise treadmill testing.

METHODS

Twenty athletes were enrolled for a standardized ramp treadmill test including transthoracic echocardiography at rest, incremental breath-by-breath spiroergometry, lactate kinetics and CW Doppler.

RESULTS

VO(2) max was 51+/-11 ml/min/kg in the adolescent cross country skiers (CI 8.2+/-1.2 l/min/m(2)) and 50+/-12 ml/min/kg in adult soccer referees (CI 7.1+/-1.2 l/min/m(2)). CW Doppler hemodynamic variables showed significant correlation with VO(2) (p<0.01, n=95) across the total of measures, with excellent correlation demonstrated for CO and CI (0.904 and 0.897), while HR and SV showed good to very good correlation with r values of 0.842 and 0.766, respectively. Correlation of the variables at peak exercise and 1 and 3 min after recovery, demonstrate that CO and SV show superior correlation with peak oxygen consumption (VO(2) max). The regression equation for VO(2) and CO(USCOM) was VO(2)=4.43CO(USCOM)-10.3.

CONCLUSION

CW Doppler measurement of cardiac output is feasible as a measure of cardiac performance during standardized treadmill testing in adolescent and adult athletes.

Serial assessment of left and right ventricular filling in patients with congestive heart failure

Serial changes in the diastolic filling of both ventricles were studied using Doppler echocardiography in 19 patients with congestive heart failure from the acute to the convalescent stage. During the acute stage, left ventricular early filling velocity (E) was high (88 +/- 17 cm/s) and atrial filling velocity (A) was low (44 +/- 23 cm/s), whereas the right ventricular E was depressed (17 +/- 8 cm/s) and A was enhanced (40 +/- 9 cm/s). As the condition improved, left ventricular E decreased (43 +/- 11 cm/s, p < 0.01) and A increased (59 +/- 24 cm/s, p < 0.01) along with a decrease in the left ventricular and atrial dimensions. In contrast to the changes in left ventricular filling, right ventricular E increased (31 +/- 10 cm/s, p < 0.01) and A decreased (32 +/- 5 cm/s, p < 0.05). There are opposite directional changes in left and right ventricular filling with clinical improvement from the acute to the convalescent stage of congestive heart failure, which suggest that the changes are related to improvement of the hemodynamic conditions of both ventricles. The changes in the right ventricular filling pattern was likely to be related to changes in right ventricular afterload, ventricular interaction and external constraint rather than a change in right ventricular filling pressure.

Loading manipulations improve the prognostic value of Doppler evaluation of mitral flow in patients with chronic heart failure

BACKGROUND

Mitral flow velocity patterns (MFVPs) evaluated by Doppler echocardiography are strong predictors of survival in various cardiac diseases. However, MFVPs may change over time according to loading conditions. We performed this prospective study to assess whether changes in MFVP induced by loading manipulations provided additional prognostic information in 173 patients with chronic heart failure.

METHODS AND RESULTS

Simultaneous Doppler echocardiographic and right-sided hemodynamic recordings were obtained at baseline in all patients, during nitroprusside infusion in the 98 patients who had a baseline restrictive (early-to-late flow velocity ratio > 1 and deceleration time < or = 130 ms) MFVP, and during passive leg lifting in the 75 patients who had a baseline nonrestrictive MFVP. Patients were categorized, according to changes in MFVP, into four groups: 61 patients with an irreversible restrictive, 37 with a reversible restrictive, 48 patients with a stable nonrestrictive, and 27 patients with an unstable nonrestrictive MFVP. Fifty patients experienced major cardiac events. Cox analysis revealed that MFVP was a strong predictor of events and that the response to loading manipulations improved its prognostic value. Patients with an irreversible restrictive MFVP had a higher event rate (51%) than patients with a reversible restrictive MFVP (19%). Among patients with a baseline nonrestrictive MFVP, those with a stable nonrestrictive MFVP had the lowest event rate (6%), whereas the event rate was 33% in patients with an unstable nonrestrictive MFVP.

CONCLUSIONS

In patients with chronic heart failure, MFVPs provide independent prognostic information. Their prognostic value can be further increased by assessment of the changes induced in them by loading manipulations.

Influence of preload reserve on stroke volume response to exercise in patients with left ventricular systolic dysfunction: a Doppler echocardiographic study

OBJECTIVES

This study evaluated the role of preload reserve in the stroke volume response to exercise in patients with left ventricular systolic dysfunction by assessing the relation between stroke volume and late left ventricular diastolic filling during exercise.

BACKGROUND

In patients with left ventricular diastolic dysfunction, the absence of left ventricular distension is the fundamental mechanism explaining the nonaugmentation of stroke volume during exercise.

METHODS

In 32 patients with left ventricular systolic dysfunction and 16 healthy control subjects, mitral and aortic velocities were recorded by Doppler echocardiography at rest and during submaximal supine bicycle exercise. Stroke volume, peak early (E) and late (A) mitral velocities, A/E ratio and end-diastolic filling were measured at rest and during exercise.

RESULTS

Stroke volume increased significantly in control subjects but did not change in patients. Peak early mitral velocity increased significantly and to the same extent in both groups, whereas peak late mitral velocity and end-diastolic filling increased significantly in both groups but more so in control subjects; the A/E ratio increased significantly in control subjects but did not change in patients. In addition, stroke volume correlated significantly with peak late mitral velocity during exercise in patients (r = 0.72, p < 0.001).

CONCLUSIONS

Compared with control subjects, patients with left ventricular systolic dysfunction exhibited limited increases in both stroke volume and late left ventricular filling during exercise. Furthermore, their stroke volume response correlated with the capacity of the left ventricle to increase late diastolic filling, that is, preload reserve.

Acute alterations of pre- and afterload: are Doppler-derived diastolic filling patterns able to differentiate the loading condition?

The net effects of acute changes in pre- and afterload on left ventricular filling, were examined by altering loading conditions in normal subjects. The specific purpose of this study was to investigate whether Doppler-derived transmitral flow patterns are able to differentiate the type of loading conditions. In 24 normal subjects (13 females, 11 males, mean age 44.1 +/- 11.5 years), the following Doppler variables were determined at baseline, after rapid volume infusion (preload increase), after nitroglycerin administration (preload decrease), during isometric exercise (afterload increase), and after application of a converting enzyme inhibitor (afterload decrease): the peak and integrated early (E, Ei) and late (A, Ai) diastolic flow velocities, their ratios (E/A, Ei/Ai), the percentage of atrial contribution (ACON), and the acceleration and deceleration times (Ac, Dc) of early filling. Reduced preload and increased afterload led to similar filling patterns characterized by a significant E and Ei decrease (p < 0.05, compared to baseline) accompanied by an A and Ai increase with a resultant reduction of E/A and Ei/Ai. Both changes increased the atrial contribution to filling and reduced Ac and Dc. Increased preload only significantly increased E and Ei, while reduced afterload did not induce any significant changes. Different loading conditions alter Doppler-derived diastolic filling patterns. However, the transmitral flow profile is not specific enough to distinguish the manner in which loading conditions have been altered.

Relation of exercise Doppler left ventricular filling to thallium lung uptake

The exercise-induced changes in left ventricular filling in patients with coronary artery disease are poorly understood. Therefore these changes were studied in relation to a noninvasive indicator of exercise pulmonary venous congestion, the lung-to-heart (L:H) ratio on symptom-limited thallium stress testing. Fifty-six patients undergoing diagnostic treadmill testing were studied; 50 of them had technically adequate Doppler recordings and became the subjects of this study. Doppler left ventricular filling was assessed with patients in the supine position both before and after exercise. Measurements included early (E) and late (A) filling velocities, their ratio, the diastolic time-velocity integral, and the diastolic filling time. The L:H ratio was considered abnormal if it was greater than the upper 95% confidence limit for a separate group of normal subjects. Twelve subjects had a documented prior myocardial infarction, 16 had stress-induced ischemia, and 20 had abnormal L:H ratios. A greater E and a longer diastolic filling time in the group with an abnormal L:H ratio were the only postexercise measurements that differed; however, E was the only filling parameter that both differed between groups after exercise (abnormal L:H group 87 +/- 25 cm/sec; normal 68 +/- 20 cm/sec; p < 0.01) and whose change from rest to after exercise was significantly different (p < 0.05). Since Doppler velocities are directly related to instantaneous gradients, the higher E in patients with evidence of exercise pulmonary congestion suggests a higher exercise early diastolic left atrial pressure.