EKG of the Month June 2008 The INFERIOR by whereitsat

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									EKG of the Month
   June 2008
The INFERIOR MI
James E. Pointer, MD
  Medical Director
EKG # 1- 42 yo female with neck pain
EKG # 2- 72 yo female with 6 hr hx DOE
EKG # 3- 38 yo female with hx TAH
                       EKG of the Month
                          June 2008
                           Answers


EKG #1
Rate:                           Imposter: Yes/No

Rhythm:                         Name:

ST Elevation: Yes/No            Interpretation/Comments:

Location of MI:

Artery:



EKG #2
Rate:                           Imposter:   Yes/No

Rhythm:                         Name:

ST Elevation: Yes/No            Interpretation/Comments:

Location of MI:

Artery:



EKG #3
Rate:                           Imposter: Yes/No

Rhythm:                         Name:

ST Elevation: Yes/No            Interpretation/Comments:

Location of MI:

Artery:
                                      EKG of the Month
                                         June 2008
                                          Answers

EKG #1
Rate:       80                                 Imposter: Yes/No

Rhythm:        Sinus                           Name: N/A

ST Elevation: Yes/No                           Interpretation/Comments: Inferolateral MI
                                               - use V4R – see accompanying literature
Location of MI: II, III, aVF, V6               note reciprocal changes in aVL

Artery: R CA vs. L circumflex



EKG #2
Rate:               88                         Imposter:   Yes/No

Rhythm: Sinus                                  Name:   N/A

ST Elevation: Yes/No                           Interpretation/Comments: Inferior MI
                                               Note ST elevation on V4R – This is a right
Location of MI: II, III, aVF, V4R              coronary artery MI (see accompanying article)
                                               Note reciprocal changes in I, aVL
Artery: R CA



EKG #3
Rate:          56                              Imposter: Yes/No

Rhythm: Sinus                                  Name: N/A

ST Elevation: Yes/No                           Interpretation/Comments: Inferolateral MI. Use
                                               V4R to determine whether R CA is occluded.
Location of MI: II, III, aVF, V3-V6            See accompanying article. Note reciprocal
                                               changes in I, aVL.
Artery: R CA vs. L circumflex
    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)
  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
The electrocardiogram continues to be a valuable, noninvasive, easily repeatable, and inexpensive means
of diagnosing many cardiac abnormalities, such as myocardial infarction, ischemia, and ventricular
hypertrophy, and it is unequaled in the analysis of cardiac arrhythmias. Also, in the past few decades the
clinical information that can be derived from the electrocardiogram has grown continually.1

Traditionally, 12 leads are recorded, 6 leads on the extremities and 6 on the precordium. This has been the
standard approach for almost half a century. The extremity leads give a more distant image of the electrical
activity of the heart. For example, leads II and III record electrical activity from the inferior wall. The
precordial leads, because they are unipolar and closer to the heart, primarily reflect the cardiac electrical
activity directly beneath the electrode. Therefore, because of their position on the chest wall, leads V2 to V6
primarily give information on the process of activation and repolarization of the anterior and lateral aspects
of the left ventricle. Lead V1 provides information on the interventricular septum and the superior part 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
   The Three ST-Segment and T-Wave Configurations That Can Be Identified by Lead V4R in
                  Patients with Acute Inferoposterior Myocardial Infarction




                      the Engl Med 1999;340:381-383
Proximal occlusion of H. N rightJcoronary artery is characterized by ST-segment elevation of at least 1
              Wellens
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.
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
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 Maastricht
6202 AZ Maastricht, the Netherlands

								
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