DESCRIPTION 
- Sudden cardiac death (SCD) is a major public health problem and responsible for ~350,000 deaths in the U.S. alone.
- Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the main mechanisms for SCD.
- Implantable cardioverter defibrillators (ICDs) are highly effective in treating VT and VF.
- Patients with significant structural heart disease are at increased risk for SCD and may be candidates for ICD therapy.
RISK FACTORS
- Ischemic cardiomyopathy, reduced systolic function (LV ejection fraction [LVEF] <35%), and nonsustained VT on Holter, with inducible sustained VT on electrophysiologic (EP) study (refractory to intravenous Procainamide) (MADIT 1 study)
- Ischemic cardiomyopathy, reduced systolic function (LVEF <30%) (MADIT 2 study)
- Ischemic or nonischemic cardiomyopathy with reduced systolic function (LVEF <30%) and class II/III heart failure (SCDHeFt study)
- Survivors of cardiac arrest not due to clearly reversible causes or patients with documented sustained VT, especially if heart disease is present (AVID, CIDS studies)
- Patients with primary electrical disorders, such as long QT syndrome or Brugada syndrome, may require an ICD.
Genetics
Certain primary electrical disorders, such as long QT syndrome or Brugada syndrome, are genetically determined and thus inherited.
PATHOPHYSIOLOGY
- VT termination often is accomplished with overdrive pacing through the ICD-antitachycardia pacing.
- Both VT and VF can be cardioverted/defibrillated successfully.
Outline
- Symptoms related to VT (palpitations, syncope) and VF (sudden collapse, sudden death)
- Antitachycardia pacing is painless.
- Cardioversion and defibrillation shocks can be quite painful.
History
- Palpitations, syncope, collapse, resuscitated sudden death
- History of prior heart disease, heart failure, or MI
Physical Exam
Possible signs of heart disease or heart failure
DIAGNOSTIC TESTS & INTERPRETATION
Imaging
Initial approach
- Echo for LV systolic function, coronary angiography
- CXR for device follow-up to assess stable lead position
Diagnostic Procedures/Surgery
Some patients may require an EP study to clarify the role of ICD therapy.
DIFFERENTIAL DIAGNOSIS
- VT need to be differentiated from supraventricular tachycardia (SVT) with wide QRS complex. SVT can be cured with catheter ablation.
- In patients with Wolff-Parkinson-White (WPW) syndrome VF is caused by atrial fibrillation and can be cured by catheter ablation.
Outline
- Optimal therapy of the underlying cardiac condition is mandatory.
- Up to 30% of ICD patients may require therapy with an antiarrhythmic drug, either to reduce the number of VT/VF episodes or to treat other arrhythmias primarily atrial fibrillation.
First Line
Often-used antiarrhythmic drugs: Amiodarone or sotalol.
ADDITIONAL TREATMENT
General Measures
ICD is implanted by a cardiac electrophysiologist with special training. Typically performed under conscious sedation in a cath-lab/EP lab setting. The implant procedure is similar to that of a pacemaker. Device testing (VF induction and defibrillation) performed after device implanted.
Referral
Often joined patient follow-up between cardiologist/primary care physician and cardiac electrophysiologist
SURGERY
- Surgical ICD implant is rare.
- Patients undergoing open heart surgery who have an ICD indication should have the device implanted transvenously after the surgery procedure.
IN-PATIENT CONSIDERATIONS
Admission Criteria
Admission for ICD implant: Typically 1 night stay, same-day discharge may be feasible in selected patients.
Discharge Criteria
- CXR and ICD interrogation performed just prior to discharge to assess stable lead position and verify proper device function and programming
- Underlying heart disease should be stable.
Outline
FOLLOW-UP RECOMMENDATIONS
- Routine follow-up (in device clinic), typically every 3 mo, is required to evaluate device function and battery status.
- After ICD shock or symptoms suggesting significant arrhythmias, ICD evaluation should be performed. The device data storage can be extremely helpful in evaluating symptoms and details of arrhythmia and device therapy delivered.
Patient Monitoring
Routine (typically every 3 mo) device interrogation, sooner if symptoms.
COMPLICATIONS
- Device implant-related complications are typically infrequent (<5%) but include infection, bleeding, vein thrombosis, pneumothorax, pericardial tamponade, stroke, MI, lead dislodgement.
- Inappropriate device therapy (antitachycardia pacing or shock therapy) occurs in 15–25% of patients. It is mostly due to sinus tachycardia or atrial arrhythmias with fast ventricular rates. Proper device programming can largely avoid such events.
Outline