Inverse Relation between Condition of Heart Failure and Intrathoracic Impedance Measured by Implantable Cardioverter Defibrillator—A case report

The patient was a 78-year-old man with dilated cardiomyopathy. His cardio-thoracic ratio was 60.4% and left ventricular ejection fraction (LVEF) was 33%. He had been repeatedly admitted for congestive heart failure. He underwent implantation of an implantable cardioverter-defibrillator (ICD) for ventricular fibrillation. We compared the values of BNP and shock impedance stored by the ICD. The correlation coefficient (p-value) between BNP and shock impedance was −0.700 (p < 0.0005), increase of BNP and shock impedance was −0.778 (p < 0.0001), percent increase of BNP and shock impedance was −0.767 (p < 0.0005). In conclusion, there is an inverse relation between BNP and shock impedance, and measurements of shock impedance may be useful in the management of congestive heart failure.