Cardiac failure is not a disease but a manifestation of underlying disease of the heart or the circulatory system.
Common causes of heart failure are coronary artery disease, cardiomyopathies, valvular heart disease and hypertensive heart disease.
A normal ECG is very unlikely in a patient of left ventricular dysfunction and hyas a negative predictive value of over 90% for presence of heart failure.
ECG abnormalities
- P wave abnormalities due to left atrial dilatation or bi atrial dilatation due to elevated end-diastolic left and right ventricular pressures.
- AV block of first or higher degress suggest underlying causes such as infiltrative cardiomyopathy.
- QRS complex duration prolongation
- Generalised low amplitude deflections of QRS complex are due to replacement of myocardium with fibrous tissue , pericardial effusion , hypothyroidism or amyloidosis.
- Left Ventricular Hypertrophy (LVH) is an independent predictor of a worse clinical outcome in patients with heart failure
- Q waves in precordial leads are an important predictor of low ejection fraction
- Absence of septal Q waves, which means it is an earliest manifestation of incomplete LBBB
- LBBB is generally associated with structural Heart disease in patients with heart failure and it usually indicates diffuse myocardial disease and fibrosis
- RBBB is not as common as that of LBBB in patients with heart failure
- ECG-CHF Triad
Relatively low limb voltage in each of limb leads
Relatively prominent QRS voltage in chest leads
poor R wave progression ( R wave less than S wave in V1 through V4 ) - ST segment depression and T wave inversion may be seen and these changes are Non-Specific
- QT interval prolongation which is a predictor of worse outcome in patients with heart failure
- Sinus Tachycardia can occur due to catecholamine surge
- Ventricular tachycardia and Ventricular fibrillation are common terminal events
Examples of ECGs of patients with CHF:-
- Ventricular Tachycardia in a patient of CHF
Electrocardiograph shows the absence of RS complexes in the precordial leads, a QS pattern in V6, and an R wave in aVR which means patient has VT.
- LBBB in a patient of CHF
ECG of a CHF patient having LBBB.