EKG of the Month June 2008 The INFERIOR MI

1. EKG of the MonthJune 2008The INFERIOR MI James E. Pointer, MD Medical Director

2. EKG # 1- 42 yo female with neck pain

3. EKG # 2- 72 yo female with 6 hr hx DOE

4. EKG # 3- 38 yo female with hx TAH

7. Clues in the detection of a right coronary (ventricular) infarct • ST Elevation II, III, aVF • ST Elevation V1 • Reciprocal ST depression I, aVL • ST elevation in III is > (higher) than ST elevation in II • ST elevation in V4R • (The first 4 of these bullets are present in EKG #3)

8. NEJM Article (Editorial 1999) • Provides a nice overview of the diagnosis and importance of using right sided precordial leads • For your scholarly use only • Do not distribute

9. The Value of the Right Precordial Leads of the Electrocardiogram The electrocardiogram continues to be a valuable, noninvasive,easily repeatable, and inexpensive means of diagnosing manycardiac abnormalities, such as myocardial infarction, ischemia,and ventricular hypertrophy, and it is unequaled in the analysisof cardiac arrhythmias. Also, in the past few decades the clinicalinformation that can be derived from the electrocardiogram hasgrown continually.1 Traditionally, 12 leads are recorded, 6 leads on the extremitiesand 6 on the precordium. This has been the standard approachfor almost half a century. The extremity leads give a more distantimage of the electrical activity of the heart. For example,leads II and III record electrical activity from the inferiorwall. The precordial leads, because they are unipolar and closerto the heart, primarily reflect the cardiac electrical activitydirectly beneath the electrode. Therefore, because of theirposition on the chest wall, leads V2 to V6 primarily give informationon the process of activation and repolarization of the anteriorand lateral aspects of the left ventricle. Lead V1 providesinformation on the interventricular septum and the superiorpart of the right ventricle. In the mid-1970s, Erhardt et al.2 showed that a true right ventricular lead (lead V4R) was of value in the diagnosis of right ventricular infarction in patients with acute inferior myocardial infarction. The diagnosis was made when ST-segment elevation was present in lead V4R. That observation was followed by several studies showing that in patients with acute inferoposterior myocardial infarction, the recording of additional right precordial leads was helpful in the detection of ischemia or infarction of the right ventricle.3,4,5 In fact, as shown in Figure 1, lead V4R emerged as a reliable marker of the site of coronary-artery occlusion in acute inferoposterior myocardial infarction, either proximal or distal to the right ventricular branch of the right coronary artery or the circumflex coronary artery. Occlusion of the proximal right coronary artery obviously leads to right ventricular involvement.6

10. The Three ST-Segment and T-Wave Configurations That Can Be Identified by Lead V4R in Patients with Acute Inferoposterior Myocardial Infarction Proximal occlusion of the right coronary artery is characterized by ST-segment elevation of at least 1 mm and a positive T wave. Distal occlusion of the right coronary artery is characterized by a positive T wave but no ST-segment elevation. Occlusion of the circumflex coronary artery is characterized by a negative T wave and ST-segment depression of at least 1 mm. Wellens H. N Engl J Med 1999;340:381-383

11. Why is diagnosing right ventricular infarction important? A primary reason is that right ventricular infarction may have important hemodynamic consequences.7 They include a lowering of cardiac output and systemic blood pressure because of dilatation and decreased compliance of the right ventricle, leading to elevated right-sided pressures and reduced left ventricular filling. Although right ventricular infarction occurs in approximately one third of patients with acute inferoposterior myocardial infarction, these hemodynamic abnormalities become clinically important in only 10 percent of such patients. Recognition is important because of the need for intravascular volume expansion and the occasional need for an infusion of dobutamine. Another problem is the high incidence (around 50 percent) of advanced atrioventricular nodal block in cases of right ventricular infarction.8 Most important, in 1993, Zehender et al.9 showed that right ventricular involvement had serious prognostic consequences in patients admitted to the hospital with acute inferoposterior myocardial infarction. They found a marked increase in mortality during hospitalization when the right ventricle was involved in the infarction. Therefore, in an editorial accompanying the article, I stressed the importance of recording lead V4R in any patient with acute inferoposterior myocardial infarction in order to select those who would most benefit from an attempt to reperfuse the ischemic area.10 That advice was given in the light of the continuing discussion about the risk–benefit ratio of reperfusion therapy in patients with acute inferoposterior myocardial infarction and the need to identify high-risk patients in this group. The importance of reperfusion in patients with right ventricular involvement was stressed not only by Zehender and associates,11 but also by Bowers et al.,12 who found that an inability to reperfuse the right coronary artery through the use of angioplasty resulted in a high rate of death during hospitalization. In a recent study of patients with inferoposterior myocardial infarction who were treated with thrombolytic therapy, Zeymer et al.13 found that the presence of ST-segment elevation of at least 0.1 mV in lead V4R was associated with increased mortality when accompanied by large ST-segment deviations in the inferior and left precordial leads. This finding is not surprising, since the larger the infarct, the higher the mortality. The message is that the magnitude of ST-segment deviation has to be considered in both the traditional leads and lead V4R in attempts to identify high-risk patients. Like O'Rourke,14 I believe that pharmacologic reperfusion or angioplasty should be performed in patients who are seen within six hours after an acute inferoposterior myocardial infarction and who have evidence of proximal occlusion in a dominant right coronary artery, as shown by the presence of substantial ST-segment deviations in the inferior leads (ST-segment elevation) and left precordial leads (ST-segment depression). A finding of concurrent ST-segment elevation in lead V4R suggests that there is proximal occlusion of a dominant right coronary artery. Attempts at reperfusion may be especially worthwhile in elderly patients.15

12. In 1985, Braat et al.16 reported on the diagnostic value of recording lead V4R during exercise testing. They showed that the presence or absence of ST-segment elevation of at least 1 mm in lead V4R during exercise could be used to predict or rule out, respectively, a clinically significant proximal stenosis in the right coronary artery. In this issue of the Journal, Michaelides and coworkers17 extend this finding and report that using the right precordial leads V3R, V4R, and V5R along with the traditional 12 leads during exercise greatly improves the sensitivity of exercise testing for the diagnosis of coronary artery disease. Using coronary angiography as the gold standard, they found that recording the right precordial leads resulted in the same diagnostic accuracy as the more expensive thallium-201 exercise scintigraphy. When evaluating the right precordial leads during exercise, the investigators considered both ST-segment elevation and depression as abnormal findings. A possible relation between the type of ST-segment change and the particular coronary artery involved was not studied. It would be interesting to know whether specific right precordial ST-segment changes can be used to identify the coronary artery that is involved. The findings of Michaelides et al.17 indicate that adding right precordial leads to the traditional electrocardiographic leads recorded during exercise improves the sensitivity of exercise electrocardiography and is less expensive than thallium-201 exercise testing. In conclusion, the right precordial leads enlarge the electrocardiographic window to include the right ventricle in addition to the left ventricle. Physicians caring for patients with acute inferoposterior myocardial infarction must understand the importance of recording lead V4R with respect to risk stratification and treatment options. Physicians should also know that recording right precordial leads during exercise is of great value in the diagnosis of coronary artery disease. Hein J.J. Wellens, M.D. Academic Hospital Maastricht6202 AZ Maastricht, the Netherlands