This document summarizes ECG manifestations in hypertrophic cardiomyopathy (HCM). Key findings include ventricular hypertrophy affecting different regions of the heart, intraventricular conduction defects, and left and/or right atrial abnormalities. Specific ECG patterns indicate septal, left ventricular, and right ventricular hypertrophy. ECG changes in HCM commonly include left ventricular hypertrophy, left atrial abnormality, pathological Q waves, and prolonged QT interval. The ECG is useful for screening populations for HCM when echocardiography is not available.

1. ECG CHANGES IN HOCM
Dr.suryakala
2nd year pg
General medicine

2. ECG Manifestations in HCM
• Ventricular hypertrophy
• Intraventricular conduction defects : Left
anterior hemiblock and bundle branch block
• Left and/or right atrial abnormality
• ECG resembling WPW syndrome
• Prolongation of QT interval
• Disturbances of cardiac rhytm

4. Ventricular hypertrophy
May affect one or more of the following regions:
• The interventricular septum
• The left free wall
• Apical and Paraseptal regions
• Right ventricle

5. SEPTAL HYPERTROPHY
• Deep and norrow q waves in leads V2-6,II and III and aVF
• Frontal plane q wave axis is directed to -1300
• Prominent initial r wave in lead V1.
This, together with findings listed under
 Indicate an initial 0.04s QRS vector which is directed
superiorly, to the right and slightly anteriorly
 Left axis deviation, mean frontal QRS axis is directed to
about –450
 S wave in lead V1 is not increased in magnitude
 The R wave in left precordial leads is of low amplitude
 Tendencty to low QRS amplitude throughout.
The manifestation of abnormal q waves in the absence of any
evidence of left free-wall hypertrophy indicates dominant
septal hypertrophy

7. Left Ventricular hypertrophy
• Deep S waves in leads V1-3
• Tall R waves in leads V5-6
• Sum of S wave in leads V1 and tall R waves in leads V6 is equal to
70mm(Normal <35mm)
• Depth of S wave in lead V1 is 30mm(Normal <20mm)
• Total QRS is >301mm(Normal <175mm)
• Amplitude of R wave in V6 is greater than V5(Reverse is normal)
• Systolic overload is reflected by inverted T waves in the left
oriented leads.
HCM is Suggested by
 Association of right atrial abnormality and left ventricular
hypertrophy
 Ths short PR interval
 Shelf like nagulation of the ST segments in standard lead I,V5 and
V6

9. APICAL HCM
• P waves are normal
• Frontal QRS axis is directed to +70
• Tall R waves in V4-6
• Epicardial injury is reflected by elevated ST
segments in lead II and leads aVF, and V2-6
• ST segments have an initial horizontality , forming
a characteristic initial ‘shelf’, with a well marked
ST-T angle in leads V3-6
• Myocardial ischemia reflected by symmetrical,
sharply, pointed inverted T waves in leads V3-6

11. RIGHT VENTRICULAR HCM
• Right axis deviation – Mean frontal plan QRS axis
is usually in the right inferior quadrant, and may
even be found in the region of +/-1800
• Right ventricular systolic overload – reflected by
tall R waves and inverted T waves in the right
precordial leads
• Right atrial enlargement – tall and peaked P
waves particularly lead II
• Complete or incomplete right bundle branch
block

12. INTRA VENTRICULAR CONDUCTUION
DEFECTS
Left anterior hemiblock –
• In about one third cases frontal QRS axis is
deviated to the left usually to -300
• Even more significant sign of HCM , if manifests in
child
Left bundle branch block –
 Incomplete heart bundle branch block is frequent
association, earliest manifestation is the
disappearance of the small normal initial q wave
in the left oriented leads.

13. Atrial abnormality
• Reflect manifestations of left/right atrial
abnormality
• Biatrial abnormality manifest with tall, wide
and notched P waves, particularly lead II
• An uncommon combination of right atrial
abnormality with left ventricular hypertrophy
or strain is very suggestive of HCM

14. Disorders of cardiac rhythm
• HCM is associated with increased incidence of
cardiac arrhytmias, even in asymptomatic
individuals
• Include Ventricular premature complexes,
paroxysmal ventricular tachycardia, which may
cause sudden cardiac death
• Less commonly, supreventricular tachycardia
and atrial fibrillation

15. EVOLUTION OF ECG CHANGES IN HCM
Common changes in order of frequency
 Left ventricular hypertrophy
 Left atrial abnormality
 Pathological q waves
 Prolongation of corrected QT interval
 Right ventricular hypertrophy
 Regression of ECG features with disappearance of pathological q
waves or disappearance of left ventricular hypertrophy In absence
of newly developed pathological q waves in minority.
 Evolution of ECG changes tends to occur more commonly in
patients with left ventricular obstruction at diagnosis, younger age
at diagnosis and with longer follow up periods

16. ROLE OF ECG IN SCREENING OF HCM
• Invaluable tool in mass screening of population where
echocardiography is not cost effective.
• Ecg manifestations may be the initial manifestation of
hemolytic crisis, appearing even before LV hypertrophy
is detectable by echocardiogram.
• ECG is more sensitive than ECHO during family
screening for identifying non-hypertrophic carriers of
certain mutations especially TnT, TnI, MBPC
• Pathological Q waves and repolarisation abnormalities
are highly specific, and are often present in children
with sarcomere protein gene mutations before the
development of echocardiographic LV hypertrophy.