Hypertrophic cardiomyopathy with atrial fibrillation
Atrial activity is seen as irregular fibrillary waves suggesting atrial fibrillation. The QRS complexes have a large amplitude in chest leads overlapping between the leads. Tall R waves in lateral leads and deep S waves in anterior leads along with gross ST segment depression with T wave inversion in lateral leads are suggestive of severe left ventricular hypertrophy. The QRS width is also increased to about 120 msec mimicking left bundle branch block. The ECG is from a case of advanced hypertrophic cardiomyopathy with atrial fibrillation. Development of atrial fibrillation leads to cardiac decompensation in hypertrophic cardiomyopathy due to loss of atrial kick. In a hypertrophied ventricle the booster effect of atrial contraction is very important for diastolic filling. Even though the contribution of atrial contraction to ventricular filling in a normal person is about 15 – 20 %, it may be over 30% in an individual with diastolic dysfunction as in hypertrophic cardiomyopathy. When the ventricular filling decreases, it reduces the cardiac output as well as an increase in the left ventricular outflow obstruction. This is because the severity of left ventricular outflow tract obstruction increases when the ventricular cavity size decreases.