Monday, June 11, 2012

ECG Interpretation Review #45 (IVCD - LAHB - Duchenne - Becker - Muscular Dystrophy - LVH - rsr' in V1 -)

The ECG shown was obtained from a 22-year-old man in a wheelchair. 
  • How would you interpret the tracing? 
  • Can you think of a clinical entity that might account for this clinical scenario? 
Figure-1 - 12-lead ECG obtained from a 22-year-old man in a wheelchair. What clinical entity is suggested? - NOTE - Enlarge by clicking on Figures - Right-Click to open in a separate window.
INTERPRETATION: The ECG shows sinus rhythm at about 70/minute. The PR interval is normal – but the QRS is prolonged to at least 0.12 second. QRS morphology in the 3 key leads (I,V1,V6) is not consistent with either left or right bundle branch block. Therefore – we would classify the conduction defect as nonspecific IVCD (IntraVentricular Conduction Delay)
  • Continuing with the interpretation – We note marked LAD (left axis deviation) consistent with LAHB (Left Anterior HemiBlock). QRS amplitude is markedly increased in lead aVL – although reliability of the ECG diagnosis of LVH (left ventricular hypertrophy) is reduced in the presence of conduction defects.
  • Regarding Q-R-S-T Changes – there are deep and wide Q waves in the high lateral leads (I,aVL). In addition – there is a small q wave in lead V2. 
  • QRS morphology in lead V1 is peculiar, as there is an rSr’s’ complex
  • This is followed by abrupt transition by lead V2, in which a disproportionately tall R wave is noted. 
  • R wave amplitude drops off by lead V3 - with persistent S waves seen throughout the remaining precordial leads. 
  • There is ST segment depression in lateral leads I and aVL which may reflect ‘strain’ from suspected LVH. That said – ST-T wave changes do not appear to be acute. 
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IMPRESSION: This ECG is clearly abnormal and highly unusual for a young adult. Given the history of a “22-year-old man in a wheelchair” should suggest the possibility of a cardiomyopathy such as Duchenne Muscular Dystrophy (DMD). There are over 20 different genetic forms of muscular dystrophy – of which DMD is the most common of these rare disorders. DMD is almost exclusively seen in males, with unfortunate outcome of progressive muscle deterioration and weakness that invariably leads to death at an early age.
  • Cardiac involvement is the rule with most muscular dystrophies. The most common ECG abnormalities in DMD (and in other muscular dystrophies) include the following: i) QRS widening from conduction defects (usually nonspecific IVCD); ii) abnormal Q waves not due to infarction (especially in lateral leads); and iii) a polyphasic rSr’s’ in lead V1 - often with surprisingly tall anterior precordial R waves. All of these features are seen in Figure-1 !
  • Please Click on Figure-2 below for brief review of clinical and ECG features of Duchenne, Becker, and other muscular dystrophies.
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ACKNOWLEDGMENT: My appreciation goes to Dr. Harsha Nagarajarao (of Cardiology Boards) for allowing me to use this tracing.
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Figure-2 - Clinical and ECG features of Muscular Dystrophy.

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