Usefulness of Tissue Doppler Imaging for the Diagnosis of Right Ventricular Myocardial Infarction and Determination of Infarct related Artery in Acute Inferior Wall Myocardial Infarction.

INTRODUCTION: In approximately half of patients with inferior wall myocardial infarction, right ventricular myocardial infarction (RVMI) develops1,2 In patients with RVMI, the risk of death in the hospital is high and major complications are greater. For early diagnosis, electrocardiography and two dimensional echocardiography are used, but these methods are occasionally insufficient. Tissue Doppler imaging (TDI) has evolved as a new technique that enables myocardial velocities to be detected and makes the quantitative assessment of the systolic and diastolic movements of myocardial walls possible. This study was designed to test the usefulness both of the right ventricular peak myocardial systolic velocity (Sm) and of the Myocardial performance index (MPI) obtained by pulsedwave TDI in the diagnosis of RVMI and in determining the infarct-related artery (IRA) in patients with acute inferior wall myocardial infarctions. Importance of identifying RVMI: Despite the initial observation of serious hemodynamic consequences of right ventricular infarction nearly two decades ago, this condition has received little clinical attention until recent years. Right ventricular infarction contributes markedly to hemodynamic instability, atrioventricular conduction block, and in-hospital mortality in patients with inferior myocardial infarctions. As compared with all clinical variables available at the time of admission,right ventricular infarction was associated with a relative risk of in-hospitalmortality of 7.7 (95 percent confidence interval, 2.6 to 23) and a risk of major in-hospital complications of 4.7 (95 percent confidence interval, 2.4 to 9). Ultimately, 95 percent of patients without evidence of right ventricular infarction at the time of admission were discharged from the hospital, as compared with only 69 percent of those in whom right ventricular infarction complicated the acute inferior myocardial infarction. METHODS: Forty patients who experienced a first acute inferior MI (mean [± SD] age, 57 ± 9 years) were prospectively assessed. An ST-segment elevation of 0.1 mV in V4- V6R lead derivations was defined as an RVMI. From the echocardiographic apical four-chamber view, the myocardial systolic velocity Sm, the peak early diastolic velocity Em , peak late diastolic velocity Am, 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 (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 fifteen patients, and the IRA in 18 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 (11.5 ± 2.5 vs 15.1 ± 3 cm/s, respectively; and 14.9 ± 2.6 cm/s, respectively [p < 0.001])., The MPI was high in the same patient groups (0.74 ± 0.13 vs 0.56 ± 0.15 in group II and 0.54 ± 0.07 in group III, respectively [p <0.001]). In the diagnosis of RVMI , and in the diagnosis of the proximal right coronary artery as the IRA, the sensitivity, specificity, negative predictive value, and positive predictive value of an Sm < 12 cm/s were calculated as 83%, 93%, 90%, and 88%. The sensitivity, specificity, negative predictive value, and positive predictive value of an MPI of > 0.70 were 78%, 91%, 88% and 82%