The Electrical Management of Cardiac Rhythm Disorders

Tachycardia

Indications for ICD Implantation

Guidelines● ACC/AHA/ESC 2006 Guidelines for Management of

Patients with Ventricular Arrhythmias and Prevention of Sudden Cardiac Death○ Full document is 100 pages○ Executive summary is 44 pages○ Available online or from SJM Library

● Class I, II (IIa and IIb), and III○ Class I: implant recommended○ Class II: evidence mixed○ Class III: implant not recommended

● Evidence levels A, B, C○ A is most stringent, C is least

Guidelines● Guidelines specify that devices should be used in patients

receiving “optimal medical therapy” meaning the most appropriate state-of-the-art pharmacological therapy for their condition

● Guidelines specify that ICDs should only be implanted in patients “who have reasonable expectation of survival with good functional status for more than one year”

Main Pathologies● LV dysfunction relating to a prior myocardial infarction

(MI)● Congenital heart disease● Metabolic and inflammatory conditions, including

○ Myocarditis○ Rheumatic disease○ Endocarditis○ Diabetes○ End stage renal failure

● Pericardial disease● Valvular heart disease

LV Dysfunction and Prior MI● Patients with coronary heart disease (CHD) are at risk of

SCD● SCD can occur in this population even if the patient does

not have severe LV dysfunction● Three main types of arrhythmias occur in this population

○ Nonsustained ventricular tachycardia (NSVT)○ Sustained VT○ Cardiac arrest associated with VT/VF

LV Dysfunction and Prior MI● ICD therapy is recommended for patients with

○ LVEF ≤ 40%○ Spontaneous NSVT or inducible to sustained

monomorphic VT● And also for patients with

○ LVEF ≤ 30% as a result of prior MI (more than 40 days earlier)

○ NYHA Class II or III

LV Dysfunction and Prior MI● What about patients who just have NSVT?

○ May be asymptomatic○ There is no evidence that suppressing NSVT confers any

mortality benefit● If the patient has sustained VT

○ Consider the symptoms○ How well does the patient tolerate the VT?○ Frequency of VT episodes

● What about patients on antiarrhythmic drugs?○ Antiarrhythmics suppress ambient arrhythmias but do not

prevent all arrhythmias○ May have pro-arrhythmic effects○ Can be prescribed together with ICD therapy

LV Dysfunction and Prior MI● Class I Indications (recommended)

○ If coronary revascularization cannot be carried out and there is evidence of prior MI and significant LV dysfunction, patients resuscitated from VF should receive an ICD

○ Primary-prevention patients with LV dysfunction due to prior MI (more than 40 days earlier) with LVEF ≤ 30-40% and NYHA Class II or III

○ Patients with LV dysfunction due to a prior MI who have hemodynamically unstable VT (LVEF scores not specified)

LV Dysfunction and Prior MI● Class I Indications (summarized)

○ Patients must have had a prior MI (at least 40 days ago)○ Patients must have LV dysfunction from that MI○ Plus they must also have

• Documented VF (resuscitation from a previous episode)

• Hemodynamically unstable VT

• NYHA Class II or III

● For clinicians○ Heart attack survivors need to know that they are at high risk

for arrhythmias, especially dangerous ventricular tachyarrhythmias

○ It is important to know the LVEF score of heart attack survivors to know if they are indicated for ICD therapy

LV Dysfunction and Prior MI● Class IIa Indications (mixed evidence, but more pro than

con)○ LV dysfunction due to prior MI (at least 40 days earlier)

• LVEF ≤ 30% to 35%• NYHA Class I

○ Recurrent sustained VT in post-MI patients with normal or near-normal ventricular function

● The guidelines also say it is a Class IIa indication ○ To prescribe adjunctive therapies for ICD patients such as

• Catheter ablation• Surgical resection• Drug therapy with amiodarone or sotalol

LV Dysfunction and Prior MI● Heart attack survivors with LV dysfunction should be

considered for an ICD if they have○ Class I

• Documented VF (resuscitation from a previous episode)• Hemodynamically unstable VT• NYHA Class II or III

○ Class IIa• NYHA Class I and• LVEF ≤ 30% to 35%

LV Dysfunction and Prior MI● Class IIb (evidence mixed, more against than for)

○ Patients with LV dysfunction from a prior MI and hemodynamically unstable VT with an LVEF ≤ 40% may receive catheter ablation or amiodarone instead of ICD therapy in the event

• They cannot be implanted with an ICD for some reason• They refuse ICD therapy

Congenital Heart Disease● Anatomic and physiologic defects in the heart● Includes a wide range of conditions● Those most associated with arrhythmias are

○ Tetralogy of Fallot○ D- transposition of the great arteries○ L- transposition of the great arteries○ Aortic stenosis○ Functional single ventricle

● SCD risk is relatively low in this patient population○ Lack of data to guide patient management decisions

● Positive EP study is necessary

Congenital Heart Disease● Class I Indications (recommended)

○ Patients with congenital heart disease who survived cardiac arrest and after evaluation of the event it is found not attributable to reversible causes

○ Patients with congenital heart disease and spontaneous sustained VT should undergo invasive hemodynamic and EP evaluation

• Catheter ablation or surgical resection to address VT• If that does not work, ICD implantation

Congenital Heart Disease● Class IIa Indications (mixed evidence, but more pro than

con)○ A congenital heart disease patient with unexplained

syncope and impaired ventricular function should undergo hemodynamic and EP evaluation. If the cause of the syncope is not reversible, the patient should receive an ICD

● Class IIb Indications (more con than pro)○ A congenital heart disease patient with ventricular

couplets or NSVT should undergo EP testing to determine the risk of arrhythmia

Congenital Heart Disease● Patients with congenital heart disease are considered suitable

candidates for ICD therapy after invasive hemodynamic and EP evaluation if○ They already survived cardiac arrest (Class I)○ They have spontaneous sustained VT and catheter ablation

or surgical resection are not desired or possible (Class I)○ They have unexplained syncope not due to a reversible

cause and impaired ventricular function (Class IIa)● It is not recommended (Class IIb) for patients with congenital

heart disease and ventricular couplets or NSVT to undergo EP testing to evaluate their risk of arrhythmias

Metabolic and Inflammatory Conditions● Myocarditis, rheumatic disease, and endocarditis● Infiltrative cardiomyopathy● Endocrine disorders and diabetes● End-stage renal failure● Obesity, dieting, anorexia

Myocarditis● Myocarditis involves inflammation of the myocardium

○ Associated with infections○ Acute myocarditis is associated with arrhythmias, including

potentially life-threatening ventricular tachyarrhythmias○ Heart block or other bradyarrhythmias may occur in acute

myocarditis (persistent heart block is rare)● Chagas disease is associated with progressive heart failure

○ Includes conduction defects up to and including complete heart block

○ Life-threatening ventricular tachyarrhythmias are possible● These conditions may require both pacing and defibrillation

Myocarditis● Class I (recommended)

○ Temporary pacing for patients with symptomatic bradycardia and/or heart block during the acute phase of myocarditis

● Class IIa (mixed but more pro than con)○ ICD implantation for patients with myocarditis but not

in the acute phase who have life-threatening ventricular tachyarrhythmias (that is, who have other ICD indications)

● Class III (not recommended)○ ICD implantation is not recommended in the acute

phase of myocarditis

Myocarditis● For patients in the acute phase of myocarditis

○ Temporary pacing may be indicated if the patient has symptomatic bradycardia and/or heart block

○ ICD implantation is not recommended (Class III)● For patients with myocarditis not in the acute phase

○ An ICD may be appropriate (Class IIa) if the patient is indicated for one according to the guidelines, in other words, if the patient has life-threatening ventricular tachyarrhythmias

○ Patients with myocarditis but otherwise no ICD indication should not get an ICD

○ However, patients with myocarditis should not be denied an ICD if they are otherwise indicated for one

Infiltrative Cardiomyopathy● Patients with infiltrative cardiomyopathy are at increased

risk for potentially life-threatening ventricular tachyarrhythmias and SCD

● Patients with infiltrative cardiomyopathy should be treated the same as patients without that condition with respect to device therapy○ If otherwise indicated for pacing, such patients should

be paced○ If otherwise indicated for an ICD, such patients should

get an ICD● This condition, in and of itself, is not an indication for a

device

Endocrine Disorders and Diabetes● Insufficient or excessive hormonal activity in these

patients can predispose patients to the risk of VT and SCD

● Endocrine disorders may accelerate the progression of underlying structural heart disease which, in turn, can increase the risk of arrhythmias

● Patients with endocrine disorders, including diabetes, should be treated the same as patients without endocrine disorders with respect to devices○ If the patient has a standard pacing indication, he or

she should be paced○ If the patient has a standard ICD indication, he or she

should get an ICD

End-Stage Renal Failure● About 40% of patients with end-stage renal failure die

from cardiovascular causes○ 20% of these deaths are attributable to SCD

● Arrhythmias should be treated conventionally in such patients (the same as patients who do not have end-stage renal failure), especially those awaiting kidney transplant○ If indicated for a pacemaker, they should be paced○ If indicated for an ICD, they should get an ICD

Obesity, Dieting, Anorexia● Eating disorders are all strongly associated with SCD● The severely obese are 40 to 60 times more likely to

experience SCD than the non-obese population● Anorexia mortality rates are 5% to 20%

○ About one-third of these are due to cardiac causes○ There are no specific data available on SCD rates

among anorectics● Such patients should be treated the same as patients

without eating disorders with respect to devices

Pericardial Disease● Ventricular arrhythmias that develop in patients with

pericardial disease should be treated in the same manner that such arrhythmias are treated in patients with other disease

● ICD and pacemaker implantation are appropriate if the patient has standard indications

● Pericardial disease is not, in and of itself, an indication for a device

Valvular Disease● Many patients with valvular disease have rhythm

disorders● There is a lack of evidence to suggest that valve

replacement or valve repair reduces the incidence of rhythm disorders in these patients

● For that reason, patients with valve disease should continue to receive appropriate treatment for their rhythm disorders, which may include device implantation

Dilated Cardiomyopathy (DCM)● Dilated cardiomyopathy occurs when the shape and

muscular quality of the heart change○ The heart becomes enlarged, flabby, floppy○ Impairs the ability of the heart to pump efficiently

● Five-year mortality rate for DCM patients is 20%○ SCD is a major contributor to that death rate

● Ventricular tachyarrhythmias are common○ SCD risk is highest among patients with other

indicators of more advanced cardiac disease, i.e. DCM patients with heart failure, etc.

Dilated Cardiomyopathy (DCM)● Class I (ICD is recommended)

○ Nonischemic DCM patients with significant LV dysfunction and sustained VT or VF

○ Nonischemic DCM patients with an LVEF ≤ 30%-35% who are NYHA Class II or III

● Class IIa (evidence mixed, but more pro than con)○ Nonischemic DCM patients with unexplained syncope

and significant LV dysfunction○ Nonischemic DCM patients with sustained VT and

normal or near-normal ventricular function● Class IIB (evidence mixed, but more against)

○ Nonischemic DCM patients with an LVEF ≤ 30-35% who are NYHA Class I

Dilated Cardiomyopathy (DCM)● Primary and secondary prevention patients in this

population● ICDs are recommend in patients with nonischemic DCM

and○ Sustained VT or VF and

• With LV dysfunction (Class I)• With normal ventricular function (Class IIa)

○ Unexplained syncope with LV dysfunction (Class IIa)○ LVEF ≤ 30-35% and

• NYHA Class II or III (Class I)• NYHA Class I (Class IIb)

Hypertrophic Cardiomyopathy (HCM)● HCM involves a stiffening of the ventricles and thickening

of the heart walls○ SCD risk is directly related to LV wall thickness○ Mortality rate is 40% or higher if the LV wall exceeds

30 mm in thickness● Increased risk of ventricular tachyarrhythmias in this

population, although many patients are asymptomatic

Hypertrophic Cardiomyopathy (HCM)● Major risk factors for HCM patients

○ Cardiac arrest (VF)○ Spontaneous, sustained VT○ Family history of premature sudden death○ Unexplained syncope○ LV wall thickness ≥ 30 mm○ Abnormal exercise blood pressure○ Nonsustained spontaneous VT

Source: Zipes et al. ACC/AHA/ESC Practice Guidelines. JACC 2003; 42: 1687-713.

Hypertrophic Cardiomyopathy (HCM)● Class I (recommended)

○ HCM patients with sustained VT or VF● Class IIa (mixed evidence, more pro than con)

○ HCM patient with one or more of the “risk factors”• VF or spontaneous sustained VT• Unexplained syncope• LV wall thickness more than 30 mm• Spontaneous NSVT• Abnormal exercise BP• Family history of premature sudden death

● Primary and secondary ICD indications for HCM patients

Arrhythmogenic RV Cardiomyopathy● ARVCM involves right-sided cardiomyopathy associated

with rhythm disorders● Sometimes called RV dysplasia● To date, no data from large randomized clinical trials to

offer evidence for therapeutic decisions● Ventricular arrhythmias occur frequently in patients with

ARVCM● ICD patients with this condition usually experience a

relatively high number of therapy deliveries

Arrhythmogenic RV Cardiomyopathy● Class I (recommended)

○ Patients with ARVCM and documented sustained VT or VF should get an ICD

● Class IIa (evidence mixed, more pro than con)○ Patients with ARVCM and one or more of the following

should get an ICD:• Extensive disease (such as those with LV involvement)• One or more family members with history of SCD• Undiagnosed syncope where VT or VF cannot be ruled out

○ If ICD implantation is not feasible in such patients, amiodarone or sotalol should be prescribed

Heart Failure (HF)● Heart failure (HF) is a syndrome rather than a disease● HF patients with some degree of LV dysfunction are at

high risk of ventricular tachyarrhythmias○ SCD may account for as much as half of deaths in this

population○ Biventricular pacing (CRT) reduces morbidity in this

population and one study (CARE-HF) showed it improved mortality

○ However, CRT without defibrillation in this population remains controversial

Heart Failure (HF)● Class I (recommended)

○ Patients with an LVEF ≤ 40% who have survived VF or hemodynamically unstable VT should get an ICD

○ Patients with LV dysfunction due to a prior MI (more than 40 days earlier) with an LVEF ≤ 30%-40% and NYHA Class II or III

○ Patients with nonischemic heart disease, an LVEF ≤ 30%-35% and NYHA Class II or III

○ Amiodarone, sotalol and/or beta-blockers are recommended adjuncts to ICD therapy in these patients

Heart Failure (HF)● Class IIa (evidence mixed, more pro than con)

○ Patients with NYHA Class III or IV with a QRS width > 120 ms should get a CRT-D device

○ Patients with NYHA Class I, LV dysfunction due to a prior MI, an LVEF ≤ 30% to 35%

○ HF patients with recurrent stable VT and normal or near-normal LVEF scores

○ Patients with NYHA Class III or IV, LVEF ≤ 35%, with a QRS width ≥ 160 ms (or at least 120 ms in the presence of other evidence of ventricular dyssynchrony) are indicated for a CRT device without defibrillation

Heart Failure (HF)● Class IIb (evidence mixed, more against than for)

○ Patients with nonischemic heart disease and an LVEF ≤ 30% to 35% and NYHA Class I should get an ICD

● The HF population includes both primary-prevention and secondary-prevention indications

Device Indications Based on LVEF Scores● ≤ 40%

○ Documented VT or VF (Class I)● ≤ 35%

○ NYHA Class III or IV plus QRS ≥ 160 ms or ≥ 120 with other evidence of ventricular dyssynchrony should get a CRT device without defibrillation (Class IIa)

● ≤ 30%-35%○ NYHA Class II or III with nonischemic heart disease (Class I)○ LV dysfunction from a prior MI (Class I)○ NYHA Class III or IV with a QRS > 120 ms should get a

CRT-D device with defibrillation (Class IIa)○ NYHA Class I with LV dysfunction due to a prior MI (Class

IIa)○ NYHA Class I (Class IIb)

Device Indications Based on NYHA Class● NYHA Class I

○ LV dysfunction due to a prior MI and LVEF ≤ 30%-35% (Class IIa)○ LVEF ≤ 30%-35% (Class IIb)

● NYHA Class II ○ Nonischemic heart disease and LVEF ≤ 30%-35% (Class I)

● NYHA Class III○ Nonischemic heart disease and LVEF ≤ 30%-35% (Class I)○ QRS > 120 ms and LVEF ≤ 30%-35% should get CRT-D (Class IIa)○ QRS ≥ 160 ms (or 120 ms with evidence of ventricular dyssynchrony)

and LVEF ≤ 35% should get CRT-P (Class IIa)

● NYHA Class IV is only indicated for a CRT system (CRT-P or CRT-D)○ QRS > 120 ms and LVEF ≤ 30%-35% should get CRT-D (Class IIa)○ QRS ≥ 160 ms (or 120 ms with evidence of ventricular dyssynchrony)

and LVEF ≤ 35% should get CRT-P (Class IIa)

Genetic Arrhythmia Syndromes● Some patients have genetic conditions that put them at

increased risk of ventricular tachyarrhythmias and SCD even though they have no structural heart damage or other conventional risk factors○ Long QT Syndrome○ Brugada Syndrome

● Relatively rare● Increased attention and study

Long QT Syndrome (LQTS)● Hereditary disorder characterized by abnormally

prolonged QT segment on the ECG● Patients are at high risk of cardiac events

○ Syncope○ Dangerous ventricular arrhythmias○ SCD

● Affects patients at all ages but may be diagnosed in pediatric population

● Beta-blockers are indicated (Class I) for LQTS○ Pacing may be required if beta blockade induces

symptomatic bradycardia○ ICDs may also be indicated

LQTS Indications● Patients with Long QT Syndrome are indicated for an ICD

if○ There is a documented episode of cardiac arrest

(Class I)○ There is documented VT and/or syncope despite beta

blockade (Class IIa)● The use of an ICD as primary prevention in LQTS

patients is a Class IIb indication (mixed evidence with weight of evidence against therapy)

Brugada Syndrome● Hereditary disorder characterized by an abnormal surface

ECG● Patients have a heart that is structurally normal● Elevated risk of ventricular arrhythmias

○ Typically polymorphic VT or VF while at rest or asleep○ Increased risk of SCD○ More common in some ethnic groups than others

(Asians are more likely to have this condition than other groups)

Brugada Syndrome Indications● Patients with Brugada Syndrome should get an ICD if

○ They have documented cardiac arrest (Class I)○ They have documented VT even if it did not result in

cardiac result (Class IIa)○ There is spontaneous ST-segment elevation on the

ECG and they have experienced syncope (Class IIa)

Miscellaneous Indications● Patients with structurally normal hearts and normal or

near-normal ventricular function are indicated for an ICD (Class IIa) if they have sustained VT

● Athletes should be evaluated like other patients but with attention given to their unique level of exertion○ Carefully evaluate athletes who experience syncope!

● Geriatric patients should be treated with respect to device therapy the same as younger patients○ However, the guidelines do not recommend ICD

therapy in patients who are not likely to live for at least one year with good functional status

Pediatric Patients● Class I indications for an ICD

○ Cardiac arrest○ Documented sustained ventricular tachyarrhythmias○ Genetic high risk ○ Cardiac arrest (Class I)

● Class IIa indications for an ICD○ Spontaneous sustained ventricular arrhythmias with

impaired LV function (LVEF ≤ 35%) (Class IIa)

Conclusion● New guidelines are an attempt to standardize device therapy

in U.S.A. and Europe○ Based on recent clinical trials○ Years of experience treating SCD with devices

● However, guidelines are guidelines○ Clinical judgment must be exercised in each individual case○ Many factors come into play including

• Clinical condition• Drug regimen• Comorbid conditions or other diseases• Prognosis• Patient and family preferences