Monday, September 10, 2012

ECG Interpretation Review #51 (Chamber Enlargement - LVH - Cardiomyopathy)

The ECG shown in Figure 1 was obtained from a 50-year-old man who presented to the office with dyspnea on exertion. No chest discomfort. He is a chronic smoker with a longterm history of alcohol consumption. The patient says he, “doesn’t see doctors”. He takes no medications. There is no obvious heart failure or wheezing on exam.
  • Should the patient be admitted to the hospital because of his ECG?
  • What clinical diagnosis do you strongly suspect?
Figure 1: ECG obtained from a 50yo smoker/drinker with dyspnea on exertion. What diagnosis is suggested by this ECG? NOTE - Enlarge by clicking on Figures - Right-Click to open in a separate window.
INTERPRETATION:  The ECG shows sinus rhythm at a rate of about 85/minute. The PR and QRS intervals are normal; the QT is no more than borderline prolonged. The axis is normal (approximately +50 degrees). Beyond this point – a variety of interpretations are possible. We make the following points:

Point #1: There appears to be evidence of at least 3 chamber enlargement:
  • RAA (Right Atrial Abnormality) – is diagnosed by the tall, peaked and pointed P wave in the inferior leads (that is >2.5 mm tall in lead II).
  • LAA (Left Atrial Abnormality) – is suggested by the deep, negative component to the P wave in lead V1.
  • Voltage for LVH (Left Ventricular Hypertrophy) – is diagnosed by the finding of deepest S wave in V1 or V2 + tallest R wave in V5 or V6 ≥35mm.
  • True LV (left ventricular) chamber enlargement is strongly suggested (with ≥90% specificity) by the finding of voltage for LVH in an adult over 35 years of age when underlying heart disease is likely – IF there are ST-T wave changes consistent with “strain” (Figure 2). The difficult-to-describe ST-T wave abnormalities seen in leads V5,V6 of Figure 1 are clearly not normal findings in these lateral precordial leads. While they do not quite manifest a typical “Strain” pattern – they do qualify as a “strain equivalent” pattern that overwhelmingly favors a diagnosis of LVH in this patient.
Figure 2: Schematic depiction of LV "strain" and "strain equivalent" patterns. When either is present in addition to voltage for LVH - the specificity of the diagnosis is greatly increased.
Point #2: The QRS complex and ST segments in Figure 1 are not normal:
  • There is ST segment coving ("frowny" configuration) with some amount of ST elevation in leads V1,V2 (difficult to be sure where the J point begins in these 2 leads).
  • The ST-T waves in leads V4,V5 are clearly abnormal (with appearance of at least some T wave inversion). There is abnormal ST-T flattening in other leads.
  • In addition – the QRS complex looks abnormal in Figure 1 (with notching and slurring in several leads). That said – the QRS is really not widened, so no definite conduction defect is present.
  • In the absence of a prior ECG – We can not rule out something acute going on (given the ST coving and elevation in leads V1,V2,V3). That said – Our "sense" is that the changes seen in Figure 1 are more likely to be longstanding and not acute.  Supporting this supposition is the lack of reciprocal changes.
Point 3: The clinical diagnosis that we strongly suspect when we encounter an ECG such as seen in Figure 1 is of a cardiomyopathy (based on the history and ECG findings of abnormal though not necessarily prolonged QRS complex; multi-chamber enlargement; and clearly abnormal ST-T wave morphology).
  • We would not necessarily admit this patient to the hospital on the sole basis of this ECG.  We would obviously feel better IF we could find an old ECG showing similar changes.  We'd use clinical judgement in the context of the clinical setting to guide our decision. 
  • This patient would most likely be admitted to the hospital IF he presented in the middle of the night to an ED (Emergency Department).  IF he however presented to the office without any objective evidence of heart failure and without any chest discomfort – and his dyspnea was not new, not severe, and associated with a good office oxygen saturation – we would probably feel comfortable managing his presumed cardiomyopathy on an ambulatory basis.  One just has to be there to decide . . .
  • See ECG Blog #73  – for more on ECG diagnosis of LVH -
  • See ECG Blog #75  – for more on Atrial Enlargement