Right ventricular asynergy during dobutamine-atropine echocardiography

Stressing the Cardiopulmonary Vascular System: The Role of Echocardiography

The cardiopulmonary vascular system represents a key determinant of prognosis in several cardiorespiratory diseases. Although right heart catheterization is considered the gold standard for assessing pulmonary hemodynamics, a comprehensive noninvasive evaluation including left and right ventricular reserve and function and cardiopulmonary interactions remains highly attractive. Stress echocardiography is crucial in the evaluation of many cardiac conditions, typically coronary artery disease but also heart failure and valvular heart disease. In stress echocardiographic applications beyond coronary artery disease, the assessment of the cardiopulmonary vascular system is a cornerstone. The possibility of coupling the left and right ventricles with the pulmonary circuit during stress can provide significant insight into cardiopulmonary physiology in healthy and diseased subjects, can support the diagnosis of the etiology of pulmonary hypertension and other conditions, and can offer valuable prognostic information. In this state-of-the-art document, the topic of stress echocardiography applied to the cardiopulmonary vascular system is thoroughly addressed, from pathophysiology to different stress modalities and echocardiographic parameters, from clinical applications to limitations and future directions.

Right ventricular plasticity and functional imaging

Right ventricular (RV) function is a strong independent predictor of outcome in a number of distinct cardiopulmonary diseases. The RV has a remarkable ability to sustain damage and recover function which may be related to unique anatomic, physiologic, and genetic factors that differentiate it from the left ventricle. This capacity has been described in patients with RV myocardial infarction, pulmonary arterial hypertension, and chronic thromboembolic disease as well as post-lung transplant and post-left ventricular assist device implantation. Various echocardiographic and magnetic resonance imaging parameters of RV function contribute to the clinical assessment and predict outcomes in these patients; however, limitations remain with these techniques. Early diagnosis of RV function and better insight into the mechanisms of RV recovery could improve patient outcomes. Further refinement of established and emerging imaging techniques is necessary to aid subclinical diagnosis and inform treatment decisions.

Right ventricular involvement in patients with coronary artery disease

PURPOSE OF REVIEW

RV involvement in coronary artery disease (CAD) includes isolated infarction and involvement in left ventricular infarction. Right ventricular involvement with left ventricular infarction has unique clinical signs and symptoms, requires different management, and has worse prognosis than left ventricular infarcts without right ventricular involvement. Although the right ventricle (RV) is geometrically complex, advances in echocardiography, nuclear imaging, computed tomography, and magnetic resonance imaging technologies have helped to optimally visualize its structure and function and to better elucidate its role in CAD.

RECENT FINDINGS

Newer noninvasive imaging modalities to visualize the RV are highlighted and their emerging clinical utilities are emphasized, including three-dimensional echocardiography, tissue Doppler velocity and strain imaging, computed tomography, and MRI.

SUMMARY

The RV is often involved in CAD. Available imaging modalities demonstrate different aspects of right ventricular involvement, yielding new insights into pathophysiology, clinical care, and management. As imaging technologies widen in their scope, cardiologists will increasingly have the imaging tools to integrate information on right ventricular morphology, hemodynamics, and function, enabling appropriate care for patients with right ventricular involvement in CAD.

Role of right ventricular wall motion abnormalities in risk stratification and prognosis of patients referred for stress echocardiography

OBJECTIVES

The purpose of this study was to evaluate the prognostic value of assessing right ventricular (RV) wall motion abnormalities during stress echocardiography (SE).

BACKGROUND

The results of SE are usually interpreted based on wall motion abnormalities of the left ventricle (LV). There is increasing recognition of the prognostic importance of RV. However, RV is still a "forgotten" chamber during routine SE.

METHODS

We evaluated 2,703 patients referred for SE. The LV was evaluated on a 16-segment model 5-point scale and the RV was evaluated on a 3-segment model 5-point scale for wall motion abnormalities. An abnormal RV or LV was defined as one with new (ischemic) or fixed (infarction) wall motion abnormalities. Follow-up (2.7 +/- 1.0 years) for confirmed myocardial infarction and cardiac death (n = 122) were obtained.

RESULTS

An abnormal RV was seen in 112 patients (4%). In the presence of an abnormal LV, patients with abnormal RV had a worse prognosis than those with normal RV. Abnormal RV was a significant predictor of events (adjusted hazard ratio 2.69, 95% confidence interval 1.22 to 5.92; p = 0.014) independent of LV ischemia and ejection fraction. A forward conditional Cox model showed that peak RV wall motion score index provided incremental prognostic value over rest and conventional SE variables (global chi-square increased from 141.4 to 161.8 to 197.0; p < 0.0001 and p = 0.006, respectively).

CONCLUSIONS

In patients referred for SE, RV wall motion analysis provides prognostic value independent of LV ischemia and ejection fraction and provides incremental value over rest and conventional SE variables. Right ventricular wall motion analysis should be routinely performed in patients referred for SE for effective risk stratification.

Does Coronary Artery Size Really Matter?

OBJECTIVE

To evaluate ischemia in right ventricle (RV) in patients with small caliber of right coronary artery (RCA).

PATIENTS AND METHODS

The study population consisted of 60 consecutive patients undergoing coronary angiography within 3 months. The patients were divided into three different groups according to lumen diameter of RCA and coronary dominance. Group 1, 2, and 3 consisted of patients with small diameter of RCA, dominant RCA, and dominant circumflex artery, respectively. RV ischemia was assessed by using pulse-wave tissue Doppler sampling obtained from RV free wall close to the lateral tricuspid annulus at the apical four-chamber view during dobutamine stress echocardiography (DSE).

RESULTS

When the mean systolic velocity percentages of increase from low to peak dose dobutamine in patients with small RCA were compared to those of other groups, statistically significant difference was found between group 1 and the other groups (P = 0.007 for group 1 vs group 2; P = 0.01 for group 1 vs group 3). The mean systolic velocity at peak dobutamine dose of patients with small caliber of right coronary artery was statistically lower than the other groups (P = 0.001 for group 1 vs group 2, P < 0.001 group 1 vs group 3).

CONCLUSIONS

There are a group of patients with small diameter of RCA causing probable ischemia in RV and small caliber of RCA can really matter in these patients.

Usefulness of low-dose dobutamine stress echocardiography for the evaluation of spontaneous recovery of stunned myocardium in patients with acute right ventricular infarction

Right ventricular (RV) infarction (RVI) is usually associated with severe RV global dysfunction representing predominantly stunned myocardium that may respond favorably to reperfusion. We assessed the efficacy of low-dose dobutamine stress echocardiography (DSE), performed early in the course of a reperfused RVI, to predict the recovery of RV systolic and diastolic function in 3 months, documenting the recovery of stunned myocardium. In all, 27 patients with acute, successfully thrombolyzed RVI comprised the study population. All patients underwent standard echocardiography at baseline and 3 months later for evaluation of RV systolic and diastolic function. At day 5 DSE was performed for evaluation of RV contractile reserve. Of the total number of segments analyzed, 69% were detected as stunned. At baseline, RV systolic and diastolic indices were seriously impaired showing significant improvement at follow-up. RV wall-motion score index during DSE was positively correlated with the same index at follow-up. DSE is a safe and precise modality to predict recovery of stunned myocardium in the setting of RVI.

Right ventricular performance at rest and during stress with chronic proximal occlusion of the right coronary artery

Acute proximal right coronary artery (RCA) occlusion results in profound right ventricular (RV) ischemic dysfunction; however, chronic RV dysfunction at rest from persistent RCA occlusion is rare. We studied the responses of the right ventricle to exercise in patients with chronic proximal RCA occlusion, demonstrating preserved RV free wall motion and appropriate augmentation of ejection fraction in nearly all cases.

New parameters in identification of right ventricular myocardial infarction and proximal right coronary artery lesion

OBJECTIVE

The diagnosis of right ventricular myocardial infarction (RVMI) accompanied by acute inferior myocardial infarction (MI) is still a problem that we encounter. This study was designed to find out the usefulness both of peak myocardial systolic velocity (Sm) and of the myocardial performance index (MPI) of the right ventricle measured by pulsed-wave tissue Doppler imaging (TDI) in assessing right ventricular function.

METHODS

Sixty patients who experienced a first acute inferior MI (mean [+/- SD] age, 57 +/- 9 years) were prospectively assessed. An ST-segment elevation of >or= 0.1 mV in V(4)-V(6)R lead derivations was defined as an RVMI. From the echocardiographic apical four-chamber view, the Sm, the peak early diastolic velocity, peak late diastolic velocity, the ejection time, the isovolumetric relaxation time, and the contraction time of the right ventricle were recorded at the level of the tricuspid annulus by using TDI. Then, the MPI was calculated. The patients were classified into the following three groups, according to the localization of the infarct-related artery (IRA) detected using coronary angiography: group I, proximal right coronary artery; group II, distal right coronary artery; and group III, circumflex coronary artery.

RESULTS

RVMIs were detected in sixteen patients, and the IRA in 27 patients was the proximal right coronary artery. The right ventricular Sm was observed to be significantly low in patients with RVMIs and those in group I compared to those without RVMIs and those in groups II and III (10.9 +/- 1.3 vs 14.3 +/- 3.2 cm/s, respectively [p < 0.001]; 11.5 +/- 2.5 vs 15.1 +/- 3 cm/s, respectively; and 14.9 +/- 2.6 cm/s, respectively [p < 0.001]). In the diagnosis of RVMI, the values for sensitivity, specificity, negative predictive value, and positive predictive value of Sm < 12 cm/s were 81%, 82%, 92%, and 62% respectively, and in the diagnosis of the proximal right coronary artery as the IRA, those values were 63%, 88%, 74%, and 81%, respectively. The MPI was high in the same patient groups (0.83 +/- 0.12 vs 0.57 +/- 0.11 in those patients without RVMI, respectively, [p < 0.001]; 0.74 +/- 0.13 vs 0.56 +/- 0.15 in group II and 0.54 +/- 0.07 in group III, respectively [p < 0.001]). The sensitivity, specificity, negative predictive value, and positive predictive value of an MPI of > 0.70 in the diagnosis of RVMI were calculated as 94%, 80%, 97%, and 63%, respectively, and in the diagnosis of the proximal right coronary artery as the IRA, those values were 78%, 91%, 83%, and 88% respectively.

CONCLUSIONS

An Sm <12 cm/s and an MPI > 0.70 obtained by TDI may define RVMI concomitant with acute inferior MI, and the IRA.

Pathophysiology and management of right heart ischemia

Acute right coronary artery occlusion proximal to the right ventricular (RV) branches results in right ventricular free wall dysfunction, exerting mechanically disadvantageous effects on biventricular performance. Depressed RV systolic function decreases transpulmonary delivery of left ventricular (LV) preload, resulting in diminished cardiac output. The ischemic right ventricle is stiff, dilated, and volume dependent, resulting in pandiastolic RV dysfunction and septally mediated alterations in LV compliance, which are exacerbated by elevated intrapericardial pressure. Under these conditions, RV pressure generation and output are dependent on LV-septal contractile contributions, governed by both primary septal contraction and paradoxical septal motion. When the culprit coronary lesion is distal to the right atrial (RA) branches, augmented RA contractility enhances RV performance and optimizes cardiac output. Conversely, more proximal occlusions result in ischemic depression of RA contractility, which impairs RV filling and performance, resulting in more severe hemodynamic compromise. Bradyarrhythmias limit output generated by the rate-dependent noncompliant ventricles. Hemodynamic compromise may respond to volume resuscitation and restoration of physiologic rhythm. Vasodilators and diuretics should generally be avoided. In some patients, parenteral inotropic stimulation may be required. The right ventricle appears to be relatively resistant to infarction and recovers even after prolonged occlusion. The term RV "infarction" appears to be somewhat of a misnomer, for in most patients acute RV dysfunction represents ischemic but predominantly viable myocardium. Although RV performance improves spontaneously even in the absence of reperfusion, recovery of function may be slow and associated with high in-hospital mortality. Reperfusion enhances recovery of RV performance and improves the clinical course and survival.

Detection of exercise-induced reversible right ventricular wall motion abnormalities using echocardiographic determined tricuspid annular motion

Effects of exercise on tricuspid annular motion at the right ventricular free wall was studied by echocardiography. The results suggest that exercise-related reversible changes in tricuspid annular motion may be used to identify patients with proximal right coronary artery stenosis.

Usefulness of pulse-wave Doppler tissue sampling and dobutamine stress echocardiography for the diagnosis of right coronary artery narrowing

To study the feasibility and diagnostic accuracy of right coronary artery (RCA) narrowing by right ventricular (RV) pulse-wave Doppler tissue sampling during dobutamine stress echocardiography (DSE), 30 patients (mean age 55 +/- 9.5 years, 26 men) with suspected coronary artery disease underwent DSE (up to 40 microg/kg/min with additional atropine during submaximum heart rate responses). Pulse-wave Doppler tissue sampling of RV free walls close to the tricuspid annulus was performed in the apical 4-chamber view. The maximum velocity during the ejection phase, early, and late diastole was measured. Data from 5 consecutive beats were averaged. The measurements were repeated at rest, at low dose (10 microg/kg/min), and at peak dobutamine stress. The results were evaluated for the prediction of significant proximal or medium RCA narrowing (> or = 50% diameter stenosis, assessed by quantitative coronary angiography within the previous 3 months). A progressive increase of the ejection phase velocity (> 25% between 10 microg/kg/min and peak stress) was predictive of a normal RCA, whereas a blunted increase and/or decrease (< 25% of increase) was predictive of significant RCA narrowing: sensitivity (95% confidence intervals): 82% (68 to 96), specificity: 78% (67 to 93), positive predictive value: 69% (52 to 86), negative predictive value: 88% (75 to 100), accuracy: 79% (65 to 94). Pulse-wave Doppler tissue sampling provided analyzable data in 100%, whereas the visual assessment of gray-scale images was possible only in 90%. Thus, in patients with suspected RCA narrowing, pulse-wave Doppler tissue sampling during DSE was able to diagnose significant RCA narrowing.