Aicds

Basics

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.

Diagnosis

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

Tests

Imaging
Lab

Echo for LV systolic function, coronary angiography
CXR for device follow-up to assess stable lead position

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) syndromeVF is caused by atrial fibrillation and can be cured by catheter ablation.

Treatment

Medication

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.
Issues for 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.

Ongoing Care

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.

Additional Reading

1
AVID investigators. A comparison or antiarrhythmic drug therapy with implantable defibrillators in patients resuscitated from near fatal ventricular arrhythmias. N Engl J Med. 1997;337:1576-1583. 2
Bardy GH, Lee KL, Mark DB. Amiodarone or an implantable defibrillator for congestive heart failure. N Engl J Med. 2005;352:225-237. [View Abstract] 3
Moss AJ, Hall WJ, Cannom DS. Improved survival with an implantable defibrillator in patients with coronary artery disease at high risk for ventricular arrhythmias. N Engl J Med. 1996;335:1933-1940. [View Abstract] 4
Moss AJ, Zareba W, Hall WJ. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002;346:877-883. [View Abstract]

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