Diuretic therapy in congestive heart failure may affect the ECG in several ways

  Vigorous diuresis results in the augmentation of QRS amplitude.

  Diuretic therapy may result in the development of
hypokalemia.

      In patients under digoxin therapy,
hypokalemia eases the development of digoxin intoxication.



References

  Journal of Electrocardiology 2005;38:54-57.

  Journal of Electrocardiology 2011;44:394.e1-394.e9.





ECG 1a. The ECG above is from an 82 years-old woman with orthopnea.
Echocardiography showed mild mitral stenosis and right heart failure, but no pericardial effusion.
She has atrial fibrillation with a high ventricular response.
Diuretic and digoxin therapy were initiated.
Calibration of the ECG is 10 mm/mV but still low voltage is seen in limb leads.

Click here for a more detailed ECG




ECG 1b. After losing 7 kgs of body weight with vigorous diuresis in several days, her complaint of orthopnea disappeared.
The rhythm is still atrial fibrillation but amplitude of the QRS complexes are increased now.
Calibraiton of the ECG is still 10 mm/mV.
Digoxin effect is also seen in the above ECG (sagging-type ST segment depression in precordial leads, I, II and aVF).

Click here for a more detailed ECG