Right ventricular ejection fraction in patients with acute anterior and inferior myocardial infarction assessed by radionuclide angiography

RIGHT VENTRICLE FUNCTION IN PATIENTS WITH ANTERIOR MYOCARDIAL INFARCTION: ARE WE SURE IT IS NOT INVOLVED?

The right and left ventricle of heart are intimately connected by anatomical and functional links. Hence, acute changes in cardiac geometry and function can modify the performance and physiology of both sides of the heart, influencing each other. After a brief overview of the anatomy and related imaging techniques for the study of right ventricular function, we report a review on the interesting correlation of acute anterior myocardial infarction and right ventricular function, very often underestimated.

Right ventricular functional analysis utilizing first pass radionuclide angiography for pre-operative ventricular assist device planning: a multi-modality comparison

BACKGROUND

Advanced heart failure treated with a left ventricular assist device is associated with a higher risk of right heart failure. Many advanced heart failures patients are treated with an ICD, a relative contraindication to MRI, prior to assist device placement. Given this limitation, left and right ventricular function for patients with an ICD is calculated using radionuclide angiography utilizing planar multigated acquisition (MUGA) and first pass radionuclide angiography (FPRNA), respectively. Given the availability of MRI protocols that can accommodate patients with ICDs, we have correlated the findings of ventricular functional analysis using radionuclide angiography to cardiac MRI, the reference standard for ventricle function calculation, to directly correlate calculated ejection fractions between these modalities, and to also assess agreement between available echocardiographic and hemodynamic parameters of right ventricular function.

METHODS

A retrospective review from January 2012 through May 2014 was performed to identify advanced heart failure patients who underwent both cardiac MRI and radionuclide angiography for ventricular functional analysis. Nine heart failure patients (8 men, 1 woman; mean age of 57.0 years) were identified. The average time between the cardiac MRI and radionuclide angiography exams was 38.9 days (range: 1 - 119 days). All patients undergoing cardiac MRI were scanned using an institutionally approved protocol for ICD with no device-related complications identified. A retrospective chart review of each patient for cardiomyopathy diagnosis, clinical follow-up, and echocardiogram and right heart catheterization performed during evaluation was also performed.

RESULTS

The 9 patients demonstrated a mean left ventricular ejection fraction (LVEF) using cardiac MRI of 20.7% (12 - 40%). Mean LVEF using MUGA was 22.6% (12 - 49%). The mean right ventricular ejection fraction (RVEF) utilizing cardiac MRI was 28.3% (16 - 43%), and the mean RVEF calculated by FPRNA was 32.6% (9 - 56%). The mean discrepancy for LVEF between cardiac MRI and MUGA was 4.1% (0 - 9%), and correlation of calculated LVEF using cardiac MRI and MUGA demonstrated an R of 0.9. The mean discrepancy for RVEF between cardiac MRI and FPRNA was 12.0% (range: 2 - 24%) with a moderate correlation (R = 0.5). The increased discrepancies for RV analysis were statistically significant using an unpaired t-test (t = 3.19, p = 0.0061). Echocardiogram parameters of RV function, including TAPSE and FAC, were for available for all 9 patients and agreement with cardiac MRI demonstrated a kappa statistic for TAPSE of 0.39 (95% CI of 0.06 - 0.72) and for FAC of 0.64 (95% of 0.21 - 1.00).

CONCLUSION

Heart failure patients are increasingly requiring left ventricular assist device placement; however, definitive evaluation of biventricular function is required due to the increased mortality rate associated with right heart failure after assist device placement. Our results suggest that FPRNA only has a moderate correlation with reference standard RVEFs calculated using cardiac MRI, which was similar to calculated agreements between cardiac MRI and echocardiographic parameters of right ventricular function. Given the need for identification of patients at risk for right heart failure, further studies are warranted to determine a more accurate estimate of RVEF for heart failure patients during pre-operative ventricular assist device planning.

Analytic Review: Right Ventricular Infarction

Right ventricular myocardial infarction (RVMI) usually occurs after occlusion of a dominant right coronary artery, and the amount of right ventricular necrosis depends on whether this occlusion occurs proximal or distal along the length of the coronary artery. In patients who have a considerable amount of right ventricular necrosis, the physical examination reveals an elevated jugular venous pressure and Kussmaul's sign. Acute hemodynamic monitoring demonstrates a disproportionate elevation of the right atrial pressure (RAP) when compared with the pulmonary artery wedge pressure (PAWP). Previously validated hemodynamic criteria for identifying hemodynamically important RVMI include an RAP greater than or equal to 10 mm Hg and a RAP: PAWP ratio greater than or equal to 0.8. These hemodynamic findings can be seen in approximately 10% of patients who are seen with acute inferior transmural myocardial infarction; the findings can be produced in another 10% of patients after volume loading.

Radionuclide angiography accurately assesses right ventricular systolic function using either the first pass or equilibrium technique. When the right ventricular ejection fraction is less than 40% and there is evidence of right ventricular wall motion abnormalities, the presence of hemodynamically important RVMI is highly likely. When a patient presents with hypotension and low cardiac index, volume therapy should be instituted initially. However, if cardiac index does not improve after RAP and PAWP have increased to greater than 20% above control values, intravenous dobutamine should be instituted without delay to restore circulatory stability. The acute and long-term prognosis of patients with RVMI is excellent as long as extensive left ventricular necrosis does not occur concomitantly. Furthermore, right ventricular systolic function has been shown to improve significantly in the recovery period so that the patient's functional capacity is not imparied.

Isolated right ventricular infarction: a diagnostic challenge

A 73-year-old woman was admitted to the emergency room due to sudden-onset dyspnoea, altered mental status and haemodynamic instability. ECG showed a junctional rhythm, T-wave inversion in I, aVL and V2-V6 (present in a previous ECG), and no ST/T changes in the right precordial leads. Transthoracic echocardiography, however, revealed a severe depression of global systolic function of right ventricle with akinesia of free wall and a normal left ventricular function. Coronary angiography showed an occlusion of the proximal segment of the right coronary artery, which was treated with balloon angioplasty, and a chronic lesion of the anterior descending artery. The patient had a good recovery and was discharged on the 14th day. Myocardial perfusion scintigraphy (stress and rest) was performed a month later, showing a fixed perfusion defect in the apex and anterior wall (medium-apical), with no signs of ischaemia.

Echocardiographic parameters as predictors of in-hospital mortality in patients with acute coronary syndrome undergoing percutaneous coronary intervention

Different ways have been used to stratify risk in acute coronary syndrome (ACS) patients. The aim of the study was to examine the usefulness of echocardiographic parameters as predictors of in-hospital outcome in patients with ACS after percutaneous coronary intervention (PCI). A data of 2030 patients with diagnosis of ACS hospitalized from December 2008 to December 2011 was used to develop a risk model based on echocardiographic parameters using the binary logistic regression. This model was independently evaluated in validation cohort prospectively (954 patients admitted during 2012). In-hospital mortality in derivation cohort was 7.73%, and 6.28% in validation cohort. Developed model has been designed with 4 independent echocardiographic predictors of in-hospital mortality: left ventricular ejection fraction (LVEF RR = 0.892; 95%CI = 0.854-0.932, P < 0.0005), aortic leaflet separation diameter (AOvs RR = 0.131; 95%CI = 0.027-0.627, P = 0.011), right ventricle diameter (RV RR = 2.675; 95%CI = 1.109-6.448, P = 0.028) and right ventricle systolic pressure (RVSP RR = 1.036; 95%CI = 1.000-1.074, P = 0.048). Model has good prognostic accuracy (AUROC = 0.84) and it retains good (AUROC = 0.78) when testing on the validation cohort. Risks for in-hospital mortality after PCI in ACS patients using echocardiographic measurements could be accurately predicted in contemporary practice. Incorporation of such developed model should facilitate research, clinical decisions, and optimizing treatment strategy in selected high risk ACS patients.

Microvascular obstruction in the right ventricle in reperfused anterior myocardial infarction. Macroscopic and pathologic evidence in a swine model

INTRODUCTION

Data on right ventricular (RV) involvement in anterior myocardial infarction are scarce. The presence of RV microvascular obstruction (MVO) in this context has not been analyzed yet. The aim of the present study was to characterize the presence of MVO in the RV in a controlled experimental swine model of reperfused anterior myocardial infarction.

MATERIALS AND METHODS

Left anterior descending (LAD) artery-perfused area (thioflavin-S staining after selective infusion in LAD artery), infarct size (lack of triphenyltetrazolium-chloride staining) and MVO (lack of thioflavin-S staining in the core of the infarcted area) in the RV were studied. A quantitative (% of the ventricular volume) and semiquantitative (number of segments involved) analysis was carried out both in the RV and LV in a 90-min left anterior descending balloon occlusion and 3-day reperfusion model in swine (n=15).

RESULTS

RV infarction and RV MVO (>1 segment) were detected in 9 (60%) and 6 (40%) cases respectively. Mean LAD-perfused area, infarct size and MVO in the RV were 33.8 ± 13%, 13.53 ± 11.7% and 3.4 ± 4.5%. Haematoxylin and eosin stains and electron microscopy of the RV-MVO areas demonstrated generalized cardiomyocyte necrosis and inflammatory infiltration along with patched hemorrhagic areas. Ex-vivo nuclear magnetic resonance (T2 sequences) microimaging of RV-MVO showed, in comparison with remote non-infarcted territories, marked hypointense zones (corresponding to necrosis, inflammation and hemorrhage) in the core of hyperintense regions (corresponding to edema).

CONCLUSIONS

In reperfused anterior myocardial infarction, MVO is frequently present in the RV. It is associated with severe histologic repercussion on the RV wall. Nuclear magnetic resonance appears as a promising technique for the noninvasive detection of this phenomenon. Further studies are warranted to evaluate the pathophysiological and clinical implications.

Right ventricular involvement in anterior myocardial infarction: a translational approach

AIMS

The aim of the present study was to evaluate the involvement of the right ventricle (RV) in reperfused anterior ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Left anterior descending (LAD)-perfused area (using thioflavin-S staining after selective infusion in proximal LAD artery, %), infarct size (using triphenyltetrazolium chloride staining, %), and salvaged myocardium (% of LAD-perfused area) in the right and left ventricle (LV) were quantified in a 90-min LAD occlusion 3-day reperfusion model in swine (n = 8). Additionally, we studied, using cardiovascular magnetic resonance, 20 patients with a first STEMI due to proximal LAD occlusion treated with primary angioplasty. Area at risk (T2-weighted sequence, %), infarct size (late enhancement imaging, %), and salvaged myocardium (% of area at risk) in the right and LV were quantified. In swine, a large LAD-perfused area was detected both in the right and LV (30 +/- 5 vs. 62 +/- 15%, P< 0.001) but more salvaged myocardium (94 +/- 6 vs. 73 +/- 11%, P< 0.001) resulted in a smaller right ventricular infarct size (2 +/- 1 vs. 16 +/- 5%, P< 0.001). Similarly, in patients a large area at risk was detected both in the right and LV (34 +/- 13 vs. 43 +/- 12%, P = 0.02). More salvaged myocardium (94 +/- 10 vs. 33 +/- 26%, P < 0.001) resulted in a smaller infarct size (2 +/- 3 vs. 30 +/- 16%, P< 0.001) in the RV.

CONCLUSION

In reperfused extensive anterior STEMI, a large area of the RV is at risk but the resultant infarct size is small.

Right ventricular infarction--diagnosis and treatment

Right ventricular infarction (RVI) as assessed by various diagnostic methods accompanies inferior-posterior wall myocardial infarction (MI) in 30 to 50% of patients. Recognition of the syndrome of RVI is important as it defines a significant clinical entity, which is associated with considerable immediate morbidity and mortality and has a well-delineated set of priorities for its management. Patients may clinically present with hypotension, elevated jugular venous pulse (JVP), and occasionally shock, all in the presence of clear lung fields. The ST-segment elevation of > or = 0.1 mV in the right precordial leads V4R is a readily available electrocardiographic sign used for diagnosis of RVI. Other diagnostic approaches for assessing RVI include echocardiography, radionuclide ventriculography, technetium pyrophosphate scanning, and hemodynamic measurements. The proper management of RVI includes volume loading to maintain adequate right ventricular preload, ionotropic support, and maintenance of atrioventricular synchrony. Reperfusion therapy should be initiated at the earliest signs of right ventricular dysfunction. Finally, complete recovery over a period of weeks to months is a rule in a majority of patients, suggesting right ventricular "stunning" rather than irreversible necrosis has occurred.

Right ventricular failure complicating heart failure: pathophysiology, significance, and management strategies

Right heart failure most commonly results from the complication of left heart failure (systolic or nonsystolic dysfunction) or pulmonary hypertension. Over the past decade, greater attention has been paid to the role of right ventricular failure in the morbidity and mortality associated with cardiomyopathy and pulmonary hypertension. The right ventricle is distinct from the left ventricle not only in its spatial localization, but also in its response to increased afterload and signaling mechanisms. This article discusses the role of right ventricular failure in the setting of heart failure as well as the clinical diagnosis and management of right ventricular failure.

Prognostic use of echocardiography 1 year after a myocardial infarction

BACKGROUND

Left ventricular (LV) and right ventricular (RV) function are known predictors of morbidity and mortality after an acute myocardial infarction (MI). However, the prognostic use of a late evaluation of cardiac function after an MI remains unclear.

METHODS

We analyzed echocardiograms obtained 1 year after MI in patients with LV dysfunction at baseline (ejection fraction [EF] < or = 40%) from 291 patients enrolled in the SAVE echocardiographic substudy who did not develop heart failure (HF) or a recurrent MI during this first year. Left ventricular EF and RV fractional area change were assessed.

RESULTS

After a median follow-up of 22 months after the 1-year echocardiogram, a low LVEF (< 30%) at 1 year was associated with an increased risk of death and/or HF (hazards ratio [HR] 2.7, 95% CI 1.3-5.3). Presence of RV dysfunction was also associated with an increased risk of death (HR 8.9, 95% CI 3.5-22.1), development of HF (HR 7.1, 95% CI 3.4-15.0), and the composite end point of death or HF (HR 7.6, 95% CI 4.1-14.2). In multivariate analyses, both low LVEF and RV dysfunction remained independently predictive of the composite end point of death or HF. Patients with biventricular dysfunction were at the greatest risk of death and/or HF (HR 19.4, 95% CI 8.2-46.0) in follow-up.

CONCLUSIONS

In a stable population of survivors of MI, impaired LV and RV function at 1 year after MI are independently and additively predictive of increased risk of HF or death.

[Right ventricular involvement in acute myocardial infarction]

Within the course of an acute posterior wall myocardial infarction there may be involvement of the right ventricle leading to right ventricular infarction. The long-term prognosis of patients with right ventricular infarction is not meaningfully compromised provided that the left ventricular function is preserved. However, in the acute phase, there may be a threefold increase in mortality if the right ventricular infarction leads to substantial right ventricular dysfunction. Consequently, right ventricular involvement should be detected as early as possible. In addition to the clinical presentation, the ECG and echocardiogram can provide decisive information. In addition to reperfusion, specific measures are employed to address the hemodynamic derangement of right ventricular dysfunction. These include administration of fluids for volume expansion to increase filling pressure and avoidance of vasodilators and diuretics.

Assessment of right ventricular function with Doppler echocardiographic indices derived from tricuspid annular motion: comparison with radionuclide angiography

OBJECTIVE

To assess right ventricular systolic function using indices derived from tricuspid annular motion, and to compare the results with right ventricular ejection fraction (RVEF) calculated from radionuclide angiography.

DESIGN

Pulsed Doppler echocardiography indices were obtained from 10 patients with a normal RVEF (group 1) and from 20 patients whose RVEF was less than 45% (group 2).

RESULTS

The patients in the two groups were similar in age, systolic blood pressure, and heart rate. There was a close correlation between the tricuspid annular motion derived indices (D wave integral (DWI), peak velocity of D wave (PVDW), and tricuspid plane systolic excursion (TPSE)) and RVEF (r = 0.72, 0.82, and 0.79, respectively). DWI was significantly higher in group 1 than in group 2. PVDW discriminated adequately between individuals with abnormal and normal right ventricular ejection fraction. The sensitivity and specificity of tricuspid annular motion derived indices were very good.

CONCLUSIONS

Indices derived from tricuspid annular motion appear to be important tools for assessing right ventricular systolic function.

Right ventricular ejection function assessed by cineangiography--Importance of bellows action

The right ventricular ejection fraction (RVEF) can be shown theoretically as a mathematical function of the percent shortening in the 3 axial dimensions of the right ventricular cavity (the septum-free wall dimension (SF), the anterior-posterior dimension (AP), and the tricuspid valve-apex dimension (TA) or the long axis dimension (LA)). There is a need to decide which mechanism is the most important for the RVEF in cases with neither obvious regional wall motion abnormalities of the left ventricle nor right ventricular overload. Forty-four consecutive subjects (34 males/10 females) were enrolled: 16 had normal hemodynamic parameters without significant coronary artery stenosis, 15 had hypertrophic cardiomyopathy and 13 had dilated cardiomyopathy. Biplane right ventricular cineangiography was performed and the percent shortening of the SF, AP, and TA or LA were measured. The percent shortening in the SF (34.8+/-14.7%) was larger than that of the AP, TA, and LA (23.2+/-8.5, 21.0+/-8.3 and 18.3+/-7.0, respectively; all p<0.001). There was a linear correlation between the percent shortening of each dimension and the RVEF. The 95% confidence interval of the regression equation from the percent shortening of the SF and RVEF was located above those from the other percent shortenings, except for a lower RVEF. These results indicate that systolic shortening of the SF (ie, bellows action) plays an important role in the RVEF except for a lower ejection fraction.

New method for calculating right ventricular ejection fraction using gated myocardial perfusion studies

BACKGROUND

Quantification of right ventricular ejection fraction (RVEF) is important in patients who have right heart failure or cor pulmonale. When Tl-201 was the primary radiotracer used to evaluate myocardial perfusion, the outline of the right ventricle could vary and was not visualized in most patients. However, visualization of the right ventricle has become easier with the use of Tc-99m-labeled myocardial perfusion agents.

PURPOSE

This study describes a new method for quantifying RVEF using gated stress myocardial perfusion (GMP) slices. The results are compared with those of first-pass radionuclide ventriculography (FPRNA) in the same patients.

METHODS

Fifty-two consecutive patients referred for routine GMP imaging were included. After administration of Tc-99m tetrofosmin, all patients underwent FPRNA using a single crystal gamma camera and a GMP study. Regions of interest (ROI) were drawn to outline the right ventricular cavity at end diastole and end systole from three pairs of GMP slices. The RVEF was calculated from the number of pixels within the ROIs. The mean RVEF obtained using FPRNA and GMP imaging was 51.8 +/- 10.8% and 51.9 +/- 12.3%, respectively. The two methods showed good correlation with r = 0.81. In addition, there was no significant difference in the RVEFs calculated using these methods (P = 0.85). Bland-Altman analysis also showed good agreement between the two methods (limits of agreement +14.4% to -14.0%, slope = 0.19). Intraobserver and interobserver correlation were evaluated by reanalyzing 12 patients using the new RVEF quantification method and were good at r = 0.87 and 0.82, respectively. Therefore, this is a new convenient method for evaluating RVEF as part of a routine tomographic gated myocardial perfusion study.

Value of ST elevation in lead III greater than lead II in inferior wall acute myocardial infarction for predicting in-hospital mortality and diagnosing right ventricular infarction

ST elevation in lead III > II has a higher sensitivity than lead V4R in diagnosing right ventricular myocardial infarction. Lead III > II is also predictive of in-hospital mortality.

ST-segment elevation in right precordial leads implies depressed right ventricular function after acute inferior myocardial infarction

BACKGROUND

The prognosis of acute inferior myocardial infarction is worse when it is complicated by right ventricular infarction. ST elevation in the right precordial leads is one of the reliable methods for detecting acute right ventricular infarction. The purpose of the study was to examine the relation between ST elevation in the right precordial electrocardiographic leads during acute inferior infarction and the severity of right ventricular systolic dysfunction.

METHODS

This study analyzed the relation between ST elevation > or = 0.1 mV in V4R and the severity of right ventricular systolic dysfunction in 43 consecutive patients (men/women: 35/8; average age 62+/-9 years) with acute inferior myocardial infarction with a rapid-response Swan-Ganz catheter to measure the right ventricular ejection fraction (RVEF).

RESULTS

RVEF was significantly lower in patients with ST elevation (n = 18) than in those without (n = 25) (33%+/-6% vs 40%+/-9%, p = 0.010). If the infarct-related lesion was located in the proximal right coronary artery, RVEF tended to be lower than if the lesion was located in the distal right coronary artery or the left circumflex coronary artery (33%+/-10% vs 37%+/-9% vs 42%+/-9%, p = 0.101). Logistic regression analysis demonstrated that ST elevation in V4R was the only independent predictor of depressed RVEF (odds ratio = 5.31, 95% confidence interval = 1.28 to 22.1, p = 0.022).

CONCLUSION

ST elevation in lead V4R during acute inferior myocardial infarction predicts right ventricular systolic dysfunction.

Relations between Doppler tracings of pulmonary regurgitation and invasive hemodynamics in acute right ventricular infarction complicating inferior wall left ventricular infarction

To test the hypothesis that flow characteristics from pulmonary regurgitation (PR) can predict right ventricular (RV) involvement in patients with inferior wall acute myocardial infarction, we prospectively recorded continuous-wave Doppler tracings and right-sided cardiac hemodynamics in 48 consecutive patients with inferior wall acute myocardial infarction and PR. Right heart hemodynamics enabled the identification of 29 patients with (group 1) and 19 without (group 2) RV involvement. In patients with RV involvement, the pulmonary regurgitant flow pattern was characterized by a rapid rise in flow velocity to a peak level followed by an abrupt deceleration in mid-diastole, whereas in patients without RV involvement, the deceleration in mid-diastole was gradual. The pressure half-time of PR (PHTPR) and the lowest mid-diastolic to peak early diastolic velocity ratio were significantly lower in group 1 than in group 2 (91 +/- 31 vs 214 +/- 57 ms [p < 0.001], 0.35 +/- 0.08 vs 0.59 +/- 0.13 [p < 0.001], respectively). The best diagnostic accuracy (95%) was obtained with cut-off values of PHTPR < or = 150 ms and the lowest mid-diastolic to peak early diastolic velocity ratio < or = 0.5: sensitivity 100%, specificity 89%, positive predictive value 94%, and negative predictive value 100%. Using multiple logistic regression analysis, we found that PHTPR was the strongest predictor of RV involvement. Thus, these parameters, derived from pulmonary regurgitant tracings, are useful in the noninvasive bedside diagnosis of RV infarction.

Reproducibility of MRI-derived measurements of right ventricular volumes and myocardial mass

Magnetic resonance (MR) imaging has been shown to provide accurate measurements of right ventricular (RV) volumes and myocardial mass. The purpose of this study was to evaluate the reproducibility of MR imaging, which in clinical practice may be as important as its absolute accuracy. The reproducibility of MR imaging measurements of the right ventricle was assessed by analyzing 40 serial functional MR imaging examinations of the right ventricle with variance component analysis. Standard deviations and 95% ranges for change were: for RV myocardial mass, 5.9 and 16 g; and for RV ejection fraction, 6.0% and 16%, respectively. Reproducibility was similar for cine and spin-echo MR imaging. The intraobserver and interobserver errors were especially large, indicating that observer subjectivity is the limiting factor in the interpretation of the MR images. This study suggests that the reproducibility of RV measurements is adequate to detect RV hypertrophy and a low ejection fraction in the individual patient. For accurate follow-up examinations, whereby smaller changes are to be detected, the reproducibility of MR imaging measurements may not be sufficient. More effort is needed to improve the reproducibility of MR imaging measurements.

Right ventricular infarction

Right ventricular infarction complicates up to half of inferior left ventricular infarctions. The term represents a spectrum of disease from mild, asymptomatic right ventricular dysfunction to cardiogenic shock, and it includes transient ischemic myocardial dysfunction as well as myocardial necrosis. Right ventricular infarction is associated with considerable morbidity and mortality, and its presence defines a high-risk subgroup of patients with inferior left ventricular infarction. Diagnosis of this condition requires a high degree of suspicion based on clinical findings and the early recording of the electrocardiogram through right precordial leads, as well as elevated right-sided filling pressures out of proportion to left-sided filling pressures. The proper management of right ventricular infarction requires sustaining adequate right ventricular preload with volume loading and maintenance of atrioventricular synchrony, reduction of right ventricular afterload (particularly when left ventricular dysfunction is present), and inotropic support of the right ventricle. Early reperfusion with fibrinolytic therapy or direct angioplasty is also warranted. Survivors of right ventricular infarction generally have a restoration of normal right ventricular function with resolution of hemodynamic abnormalities.

Normal right ventricular systolic and diastolic function assessed by krypton-81m equilibrium ventriculography

Krypton-81m equilibrium ventriculography was used to study right ventricular function in 23 healthy male volunteers. Technetium-99m lung perfusion scintigraphy was employed to subtract radionuclide activity within lung during image analysis thereby enhancing image quality. The imaging technique was used to generate a time-activity curve for the right ventricle allowing the definition of indices of normal systolic and diastolic function for the right ventricle. At rest, indices of systolic ejection and diastolic filling were comparable to those previously reported for the left ventricle. Using the imaging technique, movement artifact during exercise reduces image quality and limits accurate measurement of these indices to resting studies.

Assessment of right ventricular diastolic filling in patients with coronary artery disease

To assess right ventricular (RV) diastolic filling in coronary artery disease (CAD), with special reference to the involved lesions of the coronary arteries and left ventricular (LV) systolic function, gated radionuclide ventriculography was performed at rest in 106 patients with single-vessel CAD. Based on the site of coronary arterial involvement, patients were classified into three groups: left anterior descending CAD, right CAD, and left circumflex CAD. Patients in each group were further subdivided according to normal or decreased LV ejection fraction, resulting in six groups. Seventeen normal subjects were examined as a control group. Time-activity and its first-derivative curves were computed for the right and left ventricles. RV systolic function was normally preserved in all six groups, even when LV systolic function was damaged severely. The ratio of peak RV filling rate to peak RV ejection rate was significantly decreased in all six groups compared with that in control subjects, indicating that RV filling was impaired in patients with CAD. The ratio was below the lower limit of normal in 14 (23%) of 62 patients with normal LV systolic function and in 13 (30%) of 44 patients with impaired LV systolic function. None of the control subjects showed a decreased ratio of peak RV filling rate to peak RV ejection rate. Thus, in patients with CAD, RV filling is impaired, which may be independent of the site of coronary arterial involvement and of the LV or RV systolic function.

Effects of acute, transient coronary occlusion on global and regional right ventricular function in humans

OBJECTIVES

The aim of this study was to investigate the changes in right ventricular function during acute coronary occlusion produced by inflating a coronary angioplasty balloon catheter.

BACKGROUND

Alterations in right ventricular function are well known to occur in patients with acute myocardial infarction or ischemic cardiomyopathy. However, the changes in right ventricular function resulting from acute, transient coronary occlusion of each of the major coronary arteries have been scantily studied, perhaps because of serious limitations of currently available technology.

METHODS

A newly designed, mobile, multiwire gamma camera, in combination with generator-produced tantalum-178, affords high count rate first-pass radionuclide angiography and is thus ideal for studying right ventricular function at the bedside. Accordingly, 46 patients underwent first-pass radionuclide angiography at baseline and during transient coronary occlusion induced by a coronary angioplasty balloon catheter.

RESULTS

A significant, albeit modest, decrease in global right ventricular ejection fraction occurred during occlusion of the left anterior descending (from 42.9 +/- 9.3% to 39 +/- 8.7%, p < 0.05) and left circumflex (from 44 +/- 9.1% to 38.8 +/- 7.9%, p = 0.03) coronary arteries, but diagonal artery occlusion caused no significant change in right ventricular ejection fraction. Occlusion of the right coronary artery proximal (but not distal) to the acute marginal branch caused a significant decrease in right ventricular ejection fraction (from 42.6 +/- 4.7% to 35.7 +/- 7.2%, p < 0.01). Although occlusion of the left anterior descending, left circumflex and proximal right coronary arteries all caused significant deterioration in regional right ventricular function, only proximal right coronary occlusion caused right ventricular dilation (p < 0.005).

CONCLUSIONS

Significant impairment of right ventricular function occurs during transient occlusion of the left anterior descending, left circumflex and proximal right coronary arteries, but only occlusion of the latter causes acute right ventricular dilation, probably as a result of ischemia.

Diagnosis of right ventricular acute myocardial infarction by dual isotope thallium-201 and indium-111 antimyosin SPECT imaging

To assess the diagnostic value of indium-111 antimyosin for detecting right ventricular (RV) wall acute infarction, 30 patients with electrocardiographic-documented left ventricular inferior (posterior) wall acute myocardial infarction underwent simultaneous dual isotope indium-111 antimyosin and thallium-201 single-photon emission computed tomography (SPECT) within 2 days of admission. RV necrosis was defined as uptake of indium-111 antimyosin anterior and to the right of septal thallium uptake. Twenty-nine of the 30 patients (97%) had indium-111 antimyosin uptake in the inferior, posterior or lateral walls of the left ventricle and 14 of 30 (47%) had additional RV antimyosin uptake. Three different patterns of RV uptake of indium-111 antimyosin were observed: crescent-shaped, focal and apical. Twenty-seven patients underwent gated blood pool scanning before hospital discharge. Twelve of the 14 patients with RV antimyosin uptake had gated blood pool scintigraphy and 7 of 12 had RV dysfunction; 5 had normal RV function. Except for 1 patient who had questionable RV antimyosin uptake and had RV dysfunction, no patient without RV antimyosin uptake had RV dysfunction. In summary, right and left ventricular necrosis can be detected on tomographic images of indium-111 antimyosin uptake in patients with inferior infarctions when simultaneous uptake of a perfusion tracer, thallium-201, is imaged and used as an aid to reconstruction and anatomic localization.

Estimation of right ventricular volume by modified echocardiographic subtraction method

To evaluate the accuracy and clinical utility of right ventricular volume estimated by a modified echocardiographic subtraction method versus Krebs' original subtraction method, an experiment was performed on hearts excised from 25 animals (dogs, pigs, and cows) followed by a clinical study of 41 patients with heart disease. Right ventricular volume was measured by subtracting the left ventricular volume from that of the whole heart based on echocardiographic apical two- and four-chamber views by means of the area-length method. In the animal heart study, the coefficient of variation between the right ventricular volume estimated by the modified method and the true volume was +/- 13%. The regression equation was y = 0.94x + 4.15 (r = 0.987, p less than 0.001) and showed good correlation, whereas the right ventricular volume obtained by the original method underestimated the true volume (coefficient of variation = +/- 25%, y = 0.59x + 1.11; r = 0.976, p less than 0.001). In the clinical study, the coefficient of variation between right ventricular volume estimated by the modified echocardiographic method and RV volume estimated by radionuclide ventriculography was +/- 15%. The regression equation was y = 0.80x + 13.3 (r = 0.935, p less than 0.001). This correlation was better than that obtained by the original method (coefficient of variation = +/- 16%), where the regression equation was y = 0.60x + 2.43 (r = 0.888, p less than 0.001). Thus the accuracy of the modified subtraction method was validated, and this method showed a better correlation than the original method both experimentally and clinically.

Right ventricular volumes determined by computerized thermodilution in ischaemic heart disease: effect of exercise and nitroglycerin

In 29 patients with stable ischaemic heart disease, right heart catheterization was performed to assess the effect of exercise and nitroglycerin on right ventricular volumes, which were determined by a new computerized thermodilution system. The coefficient of variation for the determination of right ventricular ejection fraction averaged 11.0 +/- 6.2% (mean +/- standard deviation) at rest and 14.6 +/- 8.1% during exercise. End-diastolic volume index increased from 90 (65-127) ml/m2 [median (range)] at rest to 101 (81-130) ml/m2 (P less than or equal to 0.0001) during exercise. Nitroglycerin reduced this parameter at rest to 77 (44-121) ml/m2 (P less than or equal to 0.05), without affecting exercise values. Resting right ventricular ejection fraction (55 [44-64]%) was diminished by both exercise (to 52 [39-62]%, P less than or equal to 0.05) and nitroglycerin (to 53 [40-65]%, P less than or equal to 0.05). Additionally, nitroglycerin reduced the exercise induced decrease of right ventricular ejection fraction from -3 (-20-10)% to -1 (-15-14)% (P less than or equal to 0.01). Nitroglycerin diminished the left-to-right interventricular end-diastolic pressure gradient, which was estimated from the difference between pulmonary capillary wedge pressure and right atrial pressure, at rest from 6 (1-17) mmHg to 5 (2-14) mmHg (P less than or equal to 0.05) and during exercise from 17 (6-31) mmHg to 14 (1-33) mmHg (P less than or equal to 0.001). It is concluded, that both exercise and nitroglycerin cause significant changes in right ventricular volumes.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of shock associated with right ventricular infarction

Various mechanisms have been proposed to explain the shock sometimes associated with right ventricular infarction, but only small numbers of patients with clinical shock have been studied. The haemodynamic profiles of seven patients with clinical cardiogenic shock after right ventricular myocardial infarction were studied prospectively. They were selected because all had a stable cardiac rhythm and none had absolute hypovolaemia during the study period. In all of them the mean right atrial pressure exceeded the pulmonary artery occlusion pressure. After treatment with varying combinations of dopamine, dobutamine, and glyceryl trinitrate (titrated to achieve the optimum haemodynamic response) the mean systemic arterial pressure increased, as did the cardiac index. There was an associated increase in the left ventricular stroke work index but the right ventricular stroke work index was unchanged. There was no significant change in heart rate, mean right atrial pressure, or pulmonary artery occlusion pressure. This suggests that the probable mechanism of the shock associated with right ventricular infarction is concomitant severe left ventricular dysfunction.

Factors associated with late onset of advanced atrioventricular block in acute Q wave inferior infarction

To elucidate the clinical characteristics associated with advanced atrioventricular (AV) block that appears relatively late (more than 24 hours) after the onset of myocardial infarction (MI), 101 patients with acute Q wave inferior MI were studied. Fourteen patients had late-onset advanced AV block, and 87 patients were free of AV block. The hospital mortality rate was 11%. Multivariate analysis was performed to determine the important variables associated with the occurrence of late advanced AV block and hospital mortality rates based on 12 clinical variables. Colloid osmotic pressure, right atrial pressure, serum potassium level, and number of segments with advanced asynergy were the significant factors associated with the occurrence of late advanced AV block, whereas advanced asynergic segments and alveolar arterial oxygen difference were important in the consideration of hospital mortality rates. Therefore not only the extent of myocardial ischemia but also the increases in the extracellular potassium level and interstitial fluid are some of the factors that are associated with the occurrence of late advanced AV block in acute inferior MI. Late advanced AV block, in itself, has no significant influence on hospital mortality rates.

Right ventricular infarction

Right ventricular infarction commonly occurs in association with acute inferior left ventricular infarction, but is uncommon when infarction involves other areas of the left ventricle. Evidence of right ventricular infarction often can be detected by physical examination, electrocardiography, echocardiography, or radionuclide ventriculography. However, hemodynamically significant infarction (i.e., hypotension or shock) is much less frequent, occurring in approximately 10% of patients with other evidence of right ventricular infarction. Right ventricular infarction increases ventricular stiffness, thereby impeding diastolic filling. This results in hemodynamic changes similar to those found in constrictive pericarditis: elevated systemic venous pressure, a Y descent greater than the X descent, and an inspiratory increase in venous pressure. The increase in venous pressure generally equals or even exceeds left atrial pressure. When hypotension or shock occurs, expansion of vascular volume is generally employed as initial therapy. In nonresponders, dobutamine or similar inotropic agents may be helpful. The prognosis during the acute phases is guarded, but, in survivors, prognosis is favorable and generally related to the extent of left ventricular involvement.

Serial evaluation of right ventricular dysfunction associated with acute inferior myocardial infarction

Right ventricular (RV) function was evaluated serially by multigated blood pool imaging in 18 patients with RV dysfunction associated with acute inferior myocardial infarction. Radionuclide ventriculograms were performed on all patients within 18 hours of chest pain and again at 10 days. In addition, 15 of 18 patients had rest and exercise radionuclide ventriculograms at 3 months. The mean resting right ventricular ejection fractions (RVEF) at admission, 10 days, and 3 months in these patients was 31.8 +/- 12.6% (SD), 46.9 +/- 11.2% (p less than 0.05), and 44.5 +/- 10.2% (p less than 0.05), while the left ventricular ejection fractions were 55.9 +/- 10.6%, 57.9 +/- 13.3%, and 53.1 +/- 11.2% (p = ns). The 3-month exercise radionuclide ventriculogram demonstrated an increase in RVEF greater than 5% in 6 of 15 patients. In eight catheterized patients, neither the location nor the severity of coronary artery narrowing nor the presence of collaterals correlated with the RV exercise response. Improvement in RV function over a 10-day interval following acute inferior myocardial infarction suggests the presence of significant reversible right ventricular dysfunction during the acute phase.

Behavior of right and left ventricles during episodes of variant angina in relation to the site of coronary vasospasm

The effects of single-vessel coronary occlusion on simultaneously evaluated right (RV) and left ventricular (LV) performance were assessed and compared with LV perfusion patterns in 25 patients with variant angina. Coronary spasm involved the right coronary artery in 15 patients (group 1) and the left anterior descending coronary artery in 10 patients (group 2). Biventricular function was assessed by radionuclide angiography under basal conditions, during spontaneous or ergonovine-induced ischemia, and after resolution of the ischemic attack. Myocardial perfusion was assessed by thallium 201 scintigraphy in 21 patients of this series during superimposable ischemic episodes. In group 1, ischemia caused RV (14 of 15 patients) and LV (13 of 15 patients) regional dysfunction with significant reduction in RV and LV ejection fractions. The interventricular spetum was involved in six of 15 patients, causing a more pronounced LV impairment. In group 2, all patients showed septal dyssynergies associated with a reduction of LV ejection fraction; absent or trivial RV involvement was observed. In both groups, LV perfusion defects were present in all patients with LV wall motion abnormalities during ischemia, matching the site of regional dyssynergies. Thus, in a group of patients with variant angina and single-vessel disease, transient occlusion of the right coronary artery directly caused RV and LV impairment; in these patients, the extent of LV but not RV dysfunction appeared related to the presence of septal ischemia. Vasospasm of the left anterior descending coronary artery consistently caused LV dysfunction not associated with secondary effects on RV systolic function.

Assessment of right ventricular function in acute inferior myocardial infarction using 133-xenon imaging

The detection of right ventricular dysfunction in acute inferior myocardial infarction is important because of its potentially serious consequences which may be remediable with the appropriate therapeutic manoeuvres. A technique has been developed to assess right ventricular function using 133-xenon. This technique was applied to 26 patients who had sustained an acute inferior myocardial infarction. Right ventricular ejection fractions ranged from 7-54%, mean 30 +/- 11%, which was significantly lower than values obtained from normal volunteers (n = 21), mean 43 +/- 5%, and patients with arteriographically proven coronary artery disease without previous myocardial infarction (n = 12), mean 39 +/- 9%, P less than 0.001, and P less than 0.001, respectively. In the patients with acute inferior myocardial infarction 18 patients (69%) had evidence of right ventricular dysfunction (right ventricular ejection fraction less than 35%). 13/26 patients (50%) had clinical evidence of right ventricular dysfunction with a mean right ventricular ejection fraction 26 +/- 11% (range 7-54%) which was significantly lower than the patients without evidence of right ventricular dysfunction, mean 35 +/- 9% (range 16-49%), P less than 0.001. The clinical signs had a sensitivity of 72% (13/18), a specificity of 87.5% (7/8) and a predictive accuracy of 76% (20/26) when compared to the imaging data.

IN CONCLUSION

(1) gated 133-xenon imaging provides a method for assessing right ventricular function in the setting of acute myocardial infarction; (2) a wide spectrum of right ventricular dysfunction occurs following inferior myocardial infarction which may not manifest itself clinically.

Clinical significance of radionuclide angiographically-determined abnormalities following acute blunt chest trauma

Abnormalities of right and left ventricular ejection fraction and segmental wall motion may be detected by radionuclide angiography (RNA) following blunt chest trauma. Of 111 patients with blunt chest trauma who were admitted to a large regional shock trauma center and underwent combined first-pass and equilibrium gated RNA, abnormalities were present in 40 (36%). These abnormalities were confined to the right ventricle in 33 patients. There was a positive association between RNA abnormalities and the presence of right bundle branch block (10 of 40, p less than 0.05) and a negative association between RNA abnormalities and the finding of rib fractures (6 of 40, p less than 0.05). The in-hospital death rate of these patients was low (3 of 40 patients with an abnormal RNA and 2 of 71 patients with a normal RNA). Follow-up RNA was performed at 10 +/- 4 days in 26 of the 40 patients with initially abnormal scans, and 22 (85%) of the 26 had reverted to normal. Thus although RNA abnormalities appear common following blunt chest trauma, among patients who survive for more than 24 hours and who undergo subsequent RNA, the complication rate is low despite an abnormal scan. We conclude that routine RNA adds little to clinical management following acute blunt chest trauma.

Diagnosis of right ventricular involvement in chronic inferior myocardial infarction by means of body surface QRS changes

ST segment elevation in right precordial leads is thought to be good predictor of right ventricular involvement in patients with acute inferior myocardial infarction. This view, however, is rapidly disappearing. Therefore, using QRS changes in body surface potential maps in the chronic phase, we have attempted to differentiate patients with or without right ventricular involvement. Thirty patients with chronic inferior myocardial infarction (2 or more months after onset) were studied, in whom 87 unipolar ECGs and right ventriculograms were recorded. The patients were then divided into three groups depending on the locations of their abnormal QRS potentials (-2SD area) exceeding the normal range (mean -2SD). In group A, the -2SD area was located predominantly on the right inferior chest, in group B on the left inferior chest, and in group N on both the right and left inferior chests equally. The results showed that group A had a lower right ventricular ejection fraction (RVEF) compared with group B (A, 40 +/- 7%; B, 53 +/- 10%; p less than .001), while there was no difference in left ventricular ejection fraction between the two groups (49 +/- 11% and 49 +/- 11%, respectively). Moreover, right ventricular asynergy occurred in 14 of the 18 patients (78%) of group A but in only one of the 10 patients (10%) of group B. Group N was presumed to be intermediate between groups A and B.(ABSTRACT TRUNCATED AT 250 WORDS)

Revascularization of the right coronary artery: influence on thermodilution right ventricular ejection fraction

This study was designed in order to evaluate the influence of right coronary artery (RCA) disease and its revascularization on right heart performance monitored by measuring thermodilution right ventricular ejection fraction (RVEF). Forty patients undergoing elective aortocoronary bypass surgery were divided into two groups: group 1, with RCA revascularization, n=20; and group 2, without RCA disease or revascularization, n=20. RVEF was measured using a pulmonary arterial catheter mounted with a fast-response thermistor and a bedside microprocessor ejection fraction computer. The major finding of the study was that myocardial revascularization with extracorporeal circulation was followed by a decrease in RVEF which was significantly more pronounced in group 1 (-13.1%) in comparison to group 2 (-5.0%). RVEF gradually increased after bypass, but did not reach baseline values. By the first postoperative day, RVEF had reached baseline values again in group 1 and had increased beyond baseline values in group 2. Traditionally measured hemodynamic parameters could not be correlated with the course of RVEF, except for cardiac index. The present study further suggests that right-sided events may have clinical effects on left-sided function. Inadequate protection of the right heart, especially in patients with RCA stenosis, may result in depression of right ventricular myocardial performance, which can be monitored serially by measuring RVEF.

Nonischemic changes in right ventricular function on exercise. Do normal volunteers differ from patients with normal coronary arteries?

Factors other than ischemia may alter right ventricular function both at rest and on exercise. Normal volunteers differ from cardiac patients with normal coronary arteries with regard to their left ventricular response to exercise. This study examined changes in right ventricular function on exercise in 21 normal volunteers and 13 patients with normal coronary arteries, using first-pass radionuclide angiography. There were large ranges of right ventricular ejection fraction in the two groups, both at rest and on exercise. Resting right ventricular ejection fraction was 40.2 +/- 10.6% (mean +/- SD) in the volunteers and 38.6 +/- 9.7% in the patients, p = not significant, and on exercise rose significantly in both groups to 46.1 +/- 9.9% and 45.8 +/- 9.7%, respectively. The difference between the groups was not significant. In both groups some subjects with high resting values showed large decreases in ejection fraction on exercise, and there were significant negative correlations between resting ejection fraction and the change on exercise, r = -0.59 (p less than 0.01) in volunteers, and r = -0.66 (p less than 0.05) in patients. Older volunteers tended to have lower rest and exercise ejection fractions, but there was no difference between normotensive and hypertensive patients in their rest or exercise values. In conclusion, changes in right ventricular function on exercise are similar in normal volunteers and in patients with normal coronary arteries. Some subjects show decreases in right ventricular ejection fraction on exercise which do not appear to be related to ischemia.

Reproducibility of determination of right ventricular ejection fraction by radionuclide imaging: assessment by the statistical method of variance components

Confidence limits for single and repeat measurements of right ventricular ejection fraction (RVEF) were established by means of a model based on the statistical method of variance components. A total of 80 subjects (age 23 to 74 years) were examined by two radionuclide methods 1) gated first-pass (fp) technique performed in a standard 30 degrees right anterior oblique projection, and 2) multigated equilibrium imaging (muga) in an individual left anterior oblique view, applying with both methods separate end-diastolic and end-systolic ventricular regions of interest. Values obtained by fp technique were clearly higher than those measured by the muga approach, and the correlation between them was only fair: RVEFmuga = 0.48 RVEFfp + 0.13; r = 0.73; SEE = 0.08. The 95% confidence limits for a single measurement were with the fp technique: 'true' RVEF = measured RVEF +/- 6 EF-units compared to +/- 16 units with the muga method. At repeat determination within an interval of four weeks, the minimal changes in measured RVEF that were statistically significant at the 5% level were with the fp technique +/- 8 units with the same observer on both occasions and +/- 9 units with different observers. Corresponding figures with the muga method were +/- 16 and +/- 22 units, respectively. The minimal changes in a subject's 'true' RVEF necessary to produce a significant change in measured RVEF were with fp technique +/- 14 units for the same observer and +/- 17 units for different observers, compared to +/- 30 and +/- 41 units with the muga method. In conclusion, the variability with the muga approach was far greater than with the fp technique and the consequent reproducibility so poor as to preclude meaningful measurement of RVEF by the muga method.

Evolutionary changes in left and right ventricular function in acute myocardial infarction

To determine the evolutionary changes in right and left ventricular function in acute myocardial infarction, 3 serial gated blood pool scans were performed in 76 patients within 24 hours (24 H), at 10 days (10 D) and 3 months (3 M) following the onset of myocardial infarction. The patients were divided into 3 groups: ANT (anterior MI), INF (inferior MI without right ventricular dysfunction) and RVF (inferior MI with right ventricular dysfunction). LVEF in ANT was significantly lower than that of INF and RVF at 24 H, 10 D and 3 M. The ratio of right ventricular volume to LV volume (RVV/LVV) was compared among 3 groups. The mean values of RVV/LVV in RVF were 1.3 through 24 H and 3 M and they were significantly higher than the other two groups. The RVV/LVV in ANT and INF were around 1.0. LVEDVI in RVF was rather smaller than that of ANT and INF. LVESVI in ANT at 24 H was significantly larger than that of INF and RVF and the mean value of LVESVI in ANT were around 60 ml/M2 from 24 H to 3 M. LVEF in ANT, RVF and INF did not increase significantly during peak exercise at 3 M. However, quantitative regional wall motion analysis revealed that regional wall motion of R2 (posterolateral wall motion) in ANT and R5 (septal wall motion) in INF decreased significantly during peak exercise. These impairments in regional wall motion might be due to the exacerbation of ischemia of non-infarcted area.

Global and regional right ventricular function after acute myocardial infarction: dependence upon site of left ventricular infarction

The relation of global and regional right and left ventricular function during the acute phase after a first myocardial infarction was assessed by first pass radionuclide angiography in 20 patients (10 after anterior and 10 after inferior myocardial infarction). The right ventricular ejection fraction did not differ significantly between the groups, but left ventricular ejection fraction was significantly depressed after anterior myocardial infarction. There was evidence of right ventricular dilatation and impaired transit in the group with inferior infarction. Five patients with anterior infarction and six with inferior infarction had abnormal right ventricular ejection fractions. Right ventricular wall motion abnormalities affected the septal wall in the group with anterior infarction and the free wall in the group with inferior infarction. The relation between right and left ventricular ejection fractions was markedly different in the two groups. In the group with anterior infarction there was a significant linear relation between right and left ventricular ejection fraction, whereas in the group with inferior infarction there was not. Thus right ventricular dysfunction commonly occurs after both anterior and inferior myocardial infarction. Right and left ventricular impairment are related after anterior myocardial infarction, but are independent after inferior myocardial infarction. Finally, the different effects of anterior and inferior myocardial infarction on right ventricular function may be explained by differences in septal and free wall involvement.