Myocardial velocities measured during adenosine, dobutamine and supine bicycle exercise: a tissue Doppler study in healthy volunteers

Hemodynamic function of the right ventricular-pulmonary vascular-left atrial unit: normal responses to exercise in healthy adults

With each heartbeat, the right ventricle (RV) inputs blood into the pulmonary vascular (PV) compartment, which conducts blood through the lungs at low pressure and concurrently fills the left atrium (LA) for output to the systemic circulation. This overall hemodynamic function of the integrated RV-PV-LA unit is determined by complex interactions between the components that vary over the cardiac cycle but are often assessed in terms of mean pressure and flow. Exercise challenges these hemodynamic interactions as cardiac filling increases, stroke volume augments, and cycle length decreases, with PV pressures ultimately increasing in association with cardiac output. Recent cardiopulmonary exercise hemodynamic studies have enriched the available data from healthy adults, yielded insight into the underlying mechanisms that modify the PV pressure-flow relationship, and better delineated the normal limits of healthy responses to exercise. This review will examine hemodynamic function of the RV-PV-LA unit using the two-element Windkessel model for the pulmonary circulation. It will focus on acute PV and LA responses that accommodate increased RV output during exercise, including PV recruitment and distension and LA reservoir expansion, and the integrated mean pressure-flow response to exercise in healthy adults. Finally, it will consider how these responses may be impacted by age-related remodeling and modified by sex-related cardiopulmonary differences. Studying the determinants and recognizing the normal limits of PV pressure-flow relations during exercise will improve our understanding of cardiopulmonary mechanisms that facilitate or limit exercise.

Assessment of ischemic myocardium by strain-rate imaging during adenosine stress echocardiography

OBJECTIVE

Strain rate (SR) provides a quantitative segmental analysis of myocardial function. However, the use of SR with stress echocardiography to determine the ischemic myocardium has not been completely investigated. The present study aimed to determine the changes in systolic function of the ischemic myocardium by strain-rate imaging (SRI) with adenosine stress echocardiography.

METHODS

Stenosis and complete occlusion of coronary arteries were produced in 11 canine models by constricting the left anterior descending coronary artery (LAD). Myocardial longitudinal strain with adenosine was measured at baseline and during ischemia and infarction.

RESULTS

Strain and SR did not differ during ischemia and infarction as compared with that at baseline in non-LAD segments or after adenosine treatment. As compared with baseline, during ischemia, LAD segments showed significantly decreased peak systolic SR (SR(peak sys)) (P < 0.05) and significantly increased ratio of postsystolic strain (epsilon(ps)) to strain during ejection time (epsilon(et)) (epsilon(ps)/epsilon(et)) (P < 0.05); epsilon(max) and epsilon(et) were reduced slightly, epsilon(ps) and the ratio of epsilon(ps) to maximal systolic strain (epsilon(max))(epsilon(ps)/epsilon(max)) were increased minimally, but had no significance(P > 0.05). During infarction, the epsilon(ps) and the ratios of epsilon(ps)/epsilon(max) and epsilon(ps)/epsilon(et) were increased markedly (P < 0.01) and epsilon(et) and SR(peak sys) decreased as compared with that at baseline and during ischemia, whereas epsilon(max) was reduced only with at baseline (P < 0.01). After adenosine treatment, in the non-LAD segments, the values of strain and SR did not change at baseline or during ischemia and infarction and in LAD segments, values did not change at baseline and during infarction. However, during ischemia, SR(peak sys) and epsilon(et) were significantly reduced (P < 0.05), whereas epsilon(ps), epsilon(ps)/epsilon(max) and epsilon(ps)/epsilon(et) were increased (P < 0.05 and < 0.01, respectively).

CONCLUSION

Combined with adenosine stress echocardiography, SRI can quantitatively differentiate the ischemic from non-ischemic myocardium. epsilon(ps)/epsilon(max) and epsilon(ps)/epsilon(et) can be used as objective indices to identify the ischemic myocardium.

Acute administration of a single dose of valsartan improves left ventricular functions: a pilot study to assess the role of tissue velocity echocardiography in patients with systemic arterial hypertension in the TVE-valsartan study I

BACKGROUND

The advent of colour-coded tissue velocity echocardiography (TVE) has now made it possible to quantify left ventricular (LV) functions in patients with systemic arterial hypertension (HTN). Hypothesis In this project, we have studied the cardiac effects of a single dose of orally administered valsartan in patients with known HTN.

METHODS

Fifty-five patients with HTN with a mean age of 56 +/- 10 years were given an early morning dose of 80 mg valsartan withholding regular antihypertensive medications on the day of investigation. TVE images, acquired on VIVID systems were digitized for postprocessing of longitudinal and radial peak systolic velocities, strain rate, and systolic and diastolic time intervals before (pre) and 5 h after (post) administration of the drug.

RESULTS

Blood pressure (mmHg) pre and post, respectively, were 147 +/- 15 versus 137 +/- 14 systolic and 90 +/- 7 versus 86 +/- 7 diastolic (all P<0.01). LV longitudinal systolic velocities (cm s(-1)) were significantly higher post in LV septum (5.7 +/- 1.1 versus 6.4 +/- 1.6; P<0.001) with similar results obtained in other LV walls. Radial strain rate (1 s(-1)) was significantly higher post compared with pre valsartan (2.1 +/- 0.6 versus 2.3 +/- 0.9; P<0.01). Regional diastolic filling and ejection times (ms) were significantly shorter post (390 +/- 122 versus 370 +/- 120 and 275 +/- 32 versus 163 +/- 36 respectively; all P<0.05).

CONCLUSIONS

Within 5 h after oral administration of valsartan, improvement in regional myocardial systolic functions could be registered. Although the changes could well be secondary to afterload reduction, additional effects of the drug, evidenced by improved strain rate that is relatively load-independent, may have contributed in this improvement.

Differing myocardial response to a single session of hemodialysis in end-stage renal disease with and without type 2 diabetes mellitus and coronary artery disease

Background

Though hemodialysis (HD) acutely improves cardiac function, the impact of background diseases like coronary artery disease (CAD) and Type 2 diabetes (DM) in the setting of end-stage renal disease (ESRD) is not known. Tissue velocity echocardiography (TVE) offers a fast choice to follow changes in myocardial function after HD in ESRD with concomitant DM and /or CAD.

Methods

46 subjects (17 with ESRD, Group 1; 15 with DM, Group 2; 14 with DM+CAD, Group 3) underwent standard and TVE prior to and shortly after HD. Besides standard Doppler variables, regional myocardial systolic and diastolic velocities, as well as systolic strain rate were post processed.

Results

Compared with pre-HD, post-HD body weight (kg) significantly decreased in all the three groups (51 ± 9 vs. 48 ± 8, 62 ± 10 vs.59 ± 10, and 61 ± 9 vs. 58 ± 9 respectively; all p < 0.01). Left ventricular end diastolic dimensions (mm) also decreased post- HD (46 ± 5 vs. 42 ± 7, 53 ± 7 vs. 50 ± 7, 51 ± 7 vs. 47 ± 8 respectively; all p < 0.01). Regional longitudinal peak systolic velocity in septum (cm/s) significantly increased post-HD in Group 1(5.7 ± 1.6 vs. 7.2 ± 2.3; p < 0.001) while remained unchanged in the other two groups. Similar trends were noted in other left ventricular walls. When the myocardial velocities (cm/s) were computed globally, the improvement was seen only in Group 1 (6.3 ± 1.5 vs. 7.9 ± 2.0; p < 0.001). Global early regional diastolic velocity (cm/s) improved in Group 1, remained unchanged in Group 2, while significantly decreased in Group 3(-5.9 ± 1.3 vs. -4.1 ± 1.8; p < 0.01). Global systolic strain rate (1/sec) increased in the first 2 Groups but remained unchanged (-0.87 ± 0.4 vs. -0.94 ± 0.3; p = ns) in Group 3.

Conclusion

A single HD session improves LV function only in ESRD without coexistent DM and/or CAD. The present data suggest that not only dialysis-dependent changes in loading conditions but also co-existent background diseases determine the myocardial response to HD.

Stress echocardiography for the diagnosis of coronary artery disease: progress towards quantification

PURPOSE OF REVIEW

This review highlights recent progress in the quantitative approach to the interpretation of stress echocardiograms. Recent literature regarding the application of tissue Doppler and strain rate imaging for the diagnosis of coronary artery disease is summarized.

RECENT FINDINGS

The high temporal and spatial resolution of tissue Doppler and strain rate imaging permit recognition of regional myocardial dysfunction. These techniques have been performed during low- and high-dose dobutamine stress echocardiography and have been applied to exercise echocardiography. During stress, the peak systolic velocity and early diastolic velocity increased to a greater degree in normal segments compared to ischemic segments. With tissue Doppler imaging, viable segments show increases in systolic velocities in contrast to infarcted segments. Presently, the feasibility of strain rate imaging is slightly less than that of conventional wall motion assessment. However, in preliminary studies, tissue Doppler parameters and especially strain rate parameters appear to offer advantages in accuracy compared to conventional wall motion assessment.

SUMMARY

Tissue Doppler and strain rate imaging offer great promise for the accurate, reproducible quantification of regional myocardial function. Further studies are indicated to prove their accuracy, efficiency, and superiority over existing methods.