Physiological Adaptation Q 168
A nurse caring for several patients in the cardiac unit is told that one is scheduled for implantation of an automatic internal cardioverter-defibrillator. Which of the following patients is most likely to have this procedure?
A. A patient admitted for myocardial infarction without cardiac muscle damage.
B. A postoperative coronary bypass patient, recovering on schedule.
C. A patient with a history of ventricular tachycardia and syncopal episodes.
D. A patient with a history of atrial tachycardia and fatigue.
Correct Answer: C. A patient with a history of ventricular tachycardia and syncopal episodes.
An automatic internal cardioverter-defibrillator delivers an electric shock to the heart to terminate episodes of ventricular tachycardia and ventricular fibrillation. This is necessary in a patient with significant ventricular symptoms, such as tachycardia resulting in syncope. Indications are usually secondary where the patient has already suffered and survived cardiac arrest due to ventricular fibrillation/ventricular tachycardia, or primary when the patient is at high risk of sudden cardiac death due to VF/ VT but has never had any such event.
Option A: A patient with myocardial infarction that resolved with no permanent cardiac damage would not be a candidate. ICD is a state of the art device that treats arrhythmias specifically those of ventricular origin like ventricular tachycardia and fibrillation. It has become the first line of defense in patients who are at high risk for sudden cardiac death (SCD) and has shown consistent survival benefit in cardiac arrest survivors (SCA), in patients with Heart failure and severe systolic dysfunction (left ventricular ejection fraction-LVEF less than or equal to 35%) as well as in patients with hypertrophic cardiomyopathy (HCM).
Option B: A patient recovering well from coronary bypass would not need the device. ICD is essentially a pacemaker with the ability to recognize abnormally fast cardiac rhythm and provide immediate treatment which can be in the form of overdrive pacing called anti-tachycardia Pacing (ATP) or shock therapy which could be synchronized or unsynchronized, depending on the recognized rhythm and the pre-programmed rhythm detection algorithm.
Option D: Atrial tachycardia is less serious and is treated conservatively with medication and cardioversion as a last resort. Secondary prophylaxis usually involves the event of cardiac arrest due to ventricular fibrillation (VF) or hemodynamically unstable, also known as pulseless, ventricular tachycardia (VT). Adequate workup and exclusion of reversible causes should be done first before deciding to put the device in, as is endorsed by the guidelines laid down by Heart Rhythm Society (HRS) and American College of Cardiology (ACC).