This document discusses sudden cardiac death (SCD), providing information on: - SCD is an unexpected death from cardiac causes within one hour of symptoms. It often occurs in people with known or unknown heart disease. - Autopsies show most SCD victims had prior heart attacks or coronary artery disease. About 92% of SCD victims do not survive. - Risk factors for SCD include age, male sex, family history of heart disease, smoking, diabetes, and high blood pressure. EKG abnormalities like prolonged QT also increase risk. - Causes of SCD include coronary artery disease, cardiomyopathies, genetic conditions, and electrical issues in the heart. The most common mechanism is

1. SUDDEN CARDIAC DEATH
(SCD/SCA)
Dr. SUNIL REDDY

2. SUDDEN CARDIAC DEATH/ARREST
• Sudden cardiac death (SCD/SCA) is an
unexpected death due to cardiac causes that
occurs in a short time period (generally within
1 hour of symptom onset) in a person with
known/unknown cardiac disease
• Patients at risk for SCD may have prodromes
of chest pain, fatigue, palpitations, and other
nonspecific complaints.

3. THE CHRONOLOGY …

4. • SCA is not a random event. Most victims do
have heart disease or other health problems,
often without being aware of it.
• As many as 75 % of people who die of SCA
show signs of a previous heart attack. Eighty
percent have signs of coronary artery disease
• Approximately 92% of those who experience
SCA do not survive.
• SCA kills more than 1,000 people a day, or one
person every 90 seconds

5. EPIDEMIOLOGY
• Nearly two thirds of cardiac arrests occur as the first
clinically manifested event or in the clinical setting of
known disease in the absence of strong risk
predictors.
• Less than 25% of the victims have high-risk markers
based on arrhythmic or hemodynamic parameters
• General patterns of heightened risk during the
morning hours, on Mondays, and during the winter
months have been described.

6. • The incidence of SCD increases markedly with age
regardless of sex or race but the proportion of deaths
that are sudden is larger in the younger age groups
• CHD is the most common substrate underlying SCD
• After a MI the most rapid rate of attrition occurs
during the first 6 to 18 months after the index event .
• A secondary delayed increase in risk occurs in post–
myocardial infarction patients 2 to 5 years after an
index event, probably related to ventricular
remodeling and heart failure.

10. SCA – INDIAN PERSPECTIVE
• Annual incidence of SCA in India is 0.55 per
1000 population
• SCA accounts for >50% of cardiovascular
deaths in India
• The peak age of SCA occurrence is between 45
and 75 years, with a higher preponderance in
men (3:1)
• Survival rate of SCA is <1%
Fortis Hospital , New Delhi - statistics

11. SOUTH INDIAN STUDY
• The proportion of SCD among total mortality in a
population in Southern India using a questionnaire-
based approach was assessed
RESULTS:
• Out of 2185 deaths, 1691 (77.4%) were recallable.
• A total of 173 (10.3%; 128 M and 45 F; mean age -
60.8 ± 14 years) deaths were adjudicated as SCD.
• Of these, 82 (47.3%) were ≤ 60 years of age.
• Prior MI, LV dysfunction and prior aborted SCD were
found in 33.5%, 22.5% and 5.7% respectively.

12. • CAD was observed in 66 (38%) and AMI in 30 (17%).
• At least 1 of 3 CAD risk factors - hypertension,
diabetes, or smoking was observed in 80.6%.
• Proportion of subjects with at least one risk factor for
CAD were similar in the age groups above and below
50 years (67.6% vs. 81.7%, p=0.065).
CONCLUSIONS:
• SCD contributed to 10.3% of overall mortality
• On an average, SCD cases were 5-8 years younger
compared to populations reported in the western
hemisphere
Rao BH et al , Contribution of sudden cardiac death to total mortality in
India - a population based study ;Int J Cardiol. 2012 Jan 26;154(2):163-7

13. RISK FACTORS OF SCD
1. GENETIC FACTORS
2. CHD RISK FACTORS
3. ARRHYTHMIAS
4. NUTRITIONAL
5. PSYCHOSOCIAL FACTORS
6. BIOMARKERS – AS RISK FACTORS

14. GENETIC CONTRIBUTORS TO SCD RISK
Genetically Based Primary Arrhythmia Disorders
Congenital long-QT interval syndrome, short-QT syndrome
Brugada syndrome
Catecholaminergic polymorphic (“idiopathic”) VT/VF
Inherited Structural Disorders with Arrhythmic SCD Risk
Hypertrophic cardiomyopathy
Right ventricular dysplasia/cardiomyopathy
Genetic Predisposition to Induced Arrhythmias and SCD
Drug-induced “acquired” LQTS (drugs, electrolytes)
Electrolyte and metabolic arrhythmogenic effects

15. RISK FACTORS COMMON TO BOTH
CHD & SCD
NON MODIFIABLE
• Age Male Gender
• F/H/O CHD Genetic Factors
MODIFIABLE
• Smoking Hypertension
• Hyperlipidemia Diabetes Mellitus
• Obesity Renal dysfunction
• Sedentary lifestyle

16. CORONARY ARTERY DISEASE
• In the Framingham Study, preexisting CAD was
associated with a 2.8- to 5.3-fold increase in risk
of SCD
• Both left ventricular dysfunction and NYHA class
were powerful risk factors for SCD in patients
with either ischemic or nonischemic
cardiomyopathy
• An LVEF of less than 30 % (due to any etiology) is
the single most powerful independent indicator
for SCD

17. ARRHYTHMIAS
• PVCs and nonsustained VT during both the
exercise and recovery phases of a stress test are
predictive of increased risk
• Arrhythmias in the recovery phase appear to
predict a higher risk than arrhythmias in the
recovery phase
• A frequency cutoff of 10 PVCs/hour as a
threshold level for increased risk is cited by most
studies

18. ECG MARKERS
• Elevated resting heart rate
• Prolonged QRS duration
• Abnormal heart rate recovery
(HRR < 12 bpm 1st min , < 22bpm after 2 min)
• Prolonged QT interval and
• Early repolarization syndrome
(horizontal or descending ST segments in inferior /
lateral leads)

19. NUTRITIONAL RISK FACTORS
• Increased consumption of n-3 polyunsaturated
fatty acids is inversely associated with SCD to a
greater extent than nonfatal MI
• Heavy alcohol consumption ( > 5 drinks per day)
is associated with an increased risk of SCD
• In contrast, light-to-moderate levels of alcohol
consumption ( < 0.5 to 1 drinks per day) may be
associated with reduced risks of SCD.
• High magnesium diet – low risk of SCD

20. PSYCHOSOCIAL
• Lower socioeconomic status
• Depression
• Anxiety
• Social isolation and
• Psychological stress
have all been linked to an increase in
cardiovascular mortality in diverse populations

21. BIOMARKERS AS RISK FACTORS
INFLAMMATORY MARKERS
• CRP IL-1 receptor
• Fibrinogen IL-6
METABOLIC MARKERS
• Aldosterone Cystatin C
• Renin Vitamin D and PTH
NEUROHORMONAL MARKERS
• BNP / NT-pro-BNP

23. CAUSES
CAUSES OF AND CONTRIBUTING FACTORS OF SCD
Coronary artery abnormalities
Hypertrophy of ventricular myocardium
Myocardial diseases and heart failure
Inflammatory, infiltrative, neoplastic, and degenerative processes
Diseases of the cardiac valves
Congenital heart disease
Electrophysiologic abnormalities
Electrical instability related to neurohumoral and CNS influences
Sudden infant death syndrome and sudden death in children
Miscellaneous causes

24. PATHOPHYSIOLOGY
• The most common electrophysiologic
mechanisms leading to SCD are tachyarrhythmias
such as ventricular fibrillation (VF) or ventricular
tachycardia (VT).
• Reentry is the most important known mechanism
of VT and VF at tissue level
• At the cellular level increased excitation or
decreased repolarization reserve of
cardiomyocytes may result in ectopic activity (eg
automaticity, triggered activity), contributing to
VT and VF initiation.

25. • At the subcellular level, altered intracellular
Ca2+ currents, altered intracellular K+ currents
(especially in ischemia), or mutations resulting
in dysfunction of a sodium channel can
increase the likelihood of VT and VF.
• Approximately 20-30% of patients with
documented sudden death events have
bradyarrhythmia or asystole at the time of
initial contact
• Sometimes an asystole and pulseless electrical
activity (PEA) may result from a sustained VT

26. • Most cases of SCD occur in patients with
structural abnormalities of the heart
• Patients who survive a myocardial infarction,
the presence of PVCs, particularly complex
forms such as multiform PVCs, short coupling
intervals (R-on-T phenomenon), or VT (salvos
of 3 or more ectopic beats), reflect an
increased risk of sudden death

27. CLINICAL FEATURES
• Patients at risk for SCD may have prodromes
of chest pain, fatigue, palpitations, and other
nonspecific complaints.
• History and associated symptoms, to some
degree depend on the underlying etiology of
SCD
• A prior history of LV impairment (ejection
fraction < 30-35%) is the most potent common
risk factor for sudden death.

28. 1. Coronary artery disease
– Previous cardiac arrest
– Syncope
– Prior myocardial infarction, esp within 6 months
– Ejection fraction less than 30-35%
– H/O frequent ventricular ectopy (>10 PVC/h or NSVT)
2. Dilated cardiomyopathy
– Previous cardiac arrest
– Syncope
– Ejection fraction less than 30-35%
– Use of inotropic medications

29. 3. Hypertrophic cardiomyopathy
– Previous cardiac arrest
– Unexplained Syncope ( recent , in young)
– Family history of one or more premature HCM-
related deaths, particularly if sudden and multiple
– Symptoms of heart failure
– Drop in SBP or ventricular ectopy upon stress
testing
– Palpitations
– Multiple, repetitive (or prolonged) nonsustained
bursts of ventricular tachycardia on serial
ambulatory (Holter) ECGs
– Massive LV hypertrophy (wall thickness, ≥30 mm),
particularly in young patients

30. 4. Valvular disease
– Valve replacement within 6 months
– Syncope
– History of frequent ventricular ectopy
– Symptoms associated with severe uncorrected
AS/MS
5. Long QT syndrome
– Family history of long QT and SCD
– Medications that prolong the QT interval
– Bilateral deafness

31. Thompson and McCullough Cardiac
Arrest Score
1. ED SBP greater than 90 mm Hg = 1 point
2. ED SBP less than 90 mm Hg = 0 points
3. Time to ROSC less than 25 minutes = 1 point
4. Time to ROSC more than 25 minutes = 0 points
5. Neurologically responsive = 1 point
6. Comatose = 0 point
Maximum score = 3 points
• Patients with a score of 3 points can be expected
to have an 89% chance of neurologic recovery
and an 82% chance of survival to discharge

32. INVESTIGATIONS
• Cardiac enzymes
• Electrolytes
• Drug
• Toxicology screen
• BNP

33. • IMAGING
– ECG
– Signal averaged ECG
(micro T wave alternans – high NPV)
– 2D ECHO
– Nuclear imaging techniques
• Coronary angiography
• Electrophysiological studies

34. THANK U

37. ARRHYTHMIA PRECEDING SCD