Sudden Cardiac Death

Question 1

What are the first, second, and third, most common causes of sudden cardiac death in young patients?

Answer 1

1. Hypertrophic Cardiomyopathy (HCM) – Most Common Cause
2. Anomalous Coronary Arteries – Second Most Common Cause
3. Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) -Third Most Common Cause

Question 2

How is Hypertrophic cardiomyopathy inherited?

Answer 2

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant genetic disorder with incomplete penetrance.

Question 3

What is the underlying pathophysiology of Hypertrophic cardiomyopathy?

Answer 3

Caused by mutations in sarcomere proteins (e.g., beta-myosin heavy chain, myosin-binding protein C), leading to myocyte disarray, fibrosis, and increased ventricular stiffness.

Question 4

What is the key histological finding in HCM?

Answer 4

Myocyte hypertrophy and disarray along with interstitial fibrosis due to sarcomere disorder.

Question 5

What is the normal interventricular thickness and how does this differ from HCM?

Answer 5

This thickness is normally < 1.1 cm and in HCM, the thickness is usually around 2 cm.

Question 6

What is the posterior wall thickness in patients with HCM?

Answer 6

This can be normal (< 1.1 cm)

Question 7

What is the classic murmur in HCM?

Answer 7

Harsh crescendo-decrescendo systolic murmur best heard at the left lower sternal border, that increases with valsalva or standing, but decreases with squatting and handgrip.

Question 8

What specific maneuvers increase symptoms or murmur in HCM and why does this occur?

Answer 8

The murmur is a mid-systolic crescendo decrescendo murmur that accentuates with standing or valsalva.

Question 9

What allows for differentiation of HCM from aortic stenosis ?

Answer 9

The murmur seen in aortic stenosis decreases with valsalva and standing, while will increase with squatting, leg raise, and handgrip.

Question 10

What is the pathophysiology of the murmur seen in HCM?

Answer 10

Due to dynamic left ventricular outflow tract (LVOT) obstruction caused by systolic anterior motion (SAM) of the mitral valve.

Question 11

What are the common symptoms associated with HCM ?

Answer 11

Dyspnea on exertion, chest pain (angina), syncope, palpitations, and sudden cardiac death (especially in young athletes).

Question 12

Sudden Cardiac Death (SCD) in HCM most commonly are due to ?

Answer 12

Most commonly due to ventricular arrhythmias (e.g., ventricular fibrillation).

Question 13

How is the diagnosis of HCM established?

Answer 13

Echocardiography showing asymmetric septal hypertrophy, systolic anterior motion (SAM) of the mitral valve, and dynamic LVOT obstruction.

Question 14

What are the common ECG Findings in HCM?

Answer 14

LVH with high voltage QRS, deep narrow Q waves in lateral leads, and T-wave inversions.

Question 15

What is the first-line medical treatment in HCM?

Answer 15

Beta-blockers to reduce heart rate and prolong diastolic filling time.

Question 16

Why are beta blockers commonly used as a first line treatment for hypertrophic cardiomyopathy?

Answer 16

Beta blockers (eg, metoprolol) are first-line pharmacologic therapy for HCM complicated by LVOT obstruction as they increase LV blood volume to reduce LVOT tract obstruction in 2 ways. First, via negative chronotropy. This increases the diastolic filling time to increase LV end-diastolic volume. Second, via negative inotropy by decreasing contractility to cause blood ejection to complete at a higher LV end-systolic volumes.

Question 17

What is the second-line medical treatment in HCM, when would this be warranted?

Answer 17

Non-dihydropyridine calcium channel blockers (verapamil) are used to medically manage HCM when beta-blockers are contraindicated. One major contraindication would be patients with asthma. Verapamil is generally preferred over diltiazem because diltiazem has some degree of systemic vasodilatory effects that are undesirable in HCM.

Question 18

There needs to be a strict avoidance of which medications in the medical management of HCM?

Answer 18

Diuretics because these will worsen LVOT obstruction.
Vasodilators like ACE inhibitors (lisinopril) and Dihydropyridine calcium channel blockers (amlodipine) because these will reduce preload and worsen obstruction. Venous dilation reduces LV preload and arterial dilation reduces afterload, both of which reduce LV blood volume and can worsen LVOT obstruction and symptoms in HCM.

Question 19

What are the indications for ICD placement in HCM?

Answer 19

History of ventricular arrhythmias, unexplained syncope, family history of SCD, massive LVH (>30 mm), or abnormal BP response to exercise.

Question 20

How is HCM differentiated from athlete’s heart?

Answer 20

HCM has abnormal diastolic function and asymmetric hypertrophy, while athlete’s heart has normal diastolic function and symmetric hypertrophy.

Question 21

What is the surgical management in HCM, and when is this called for?

Answer 21

Septal myectomy or alcohol septal ablation is primarily reserved for refractory symptoms associated with HCM, despite medical therapy.

Question 22

What restrictions need to be adhered to in the management of HCM?

Answer 22

Patients need to be advised that they should avoid competitive sports as well as high-intensity exercises due to their increased risk of sudden cardiac death.

Question 23

What is the second most common cause of sudden cardiac death in young patients?

Answer 23

Anomalous coronary artery

Question 24

What is the pathophysiology of anomalous coronary artery origin?

Answer 24

Anomalous coronary artery origin, particularly the left coronary artery originating from the right sinus of Valsalva or the right coronary artery originating from the left sinus, creates sharp curvature.

Question 25

What are the two most common types of anomalous coronary artery origin?

Answer 25

The two types of AAOCA commonly associated with SCD are the left main coronary artery originating from the right aortic sinus and the right coronary artery originating from the left aortic sinus. These defects create sharp curvature of the anomalous artery, making it less amenable to high-volume flow. In addition, the anomalous artery passes between the aorta and the pulmonary artery, making it susceptible to external compression during exercise.

Question 26

What are the clinical clues for anomalous coronary artery origin?

Answer 26

Sudden collapse or syncope during high-intensity physical activity in a previously healthy individual. The patients may have exertional chest pain or lightheadedness. Some patients experience SCD without any premonitory symptoms.

Question 27

What are the risk factors for anomalous aortic origin of a coronary artery?

Answer 27

Young athletes and military recruits (about one-third of cases).

Question 28

What diagnostic tools are used for detecting anomalous coronary artery origin?

Answer 28

Resting ECG is typically unremarkable. Transthoracic echocardiography can sometimes make the diagnosis, but it can also miss or inaccurately characterize AAOCA. CT coronary angiography or coronary magnetic resonance angiography provide the best visualization of coronary anatomy, and are the diagnostic tests of choice in patients with suspected AAOCA. CT coronary angiography and cardiac MRI are the gold standards for visualizing coronary artery anatomy and confirming diagnosis.

Question 29

What are the essential differential diagnoses for anomalous aortic origin of coronary artery ?

Answer 29

1) Hypertrophic Cardiomyopathy (HCM)

2) Congenital Long QT Syndrome (LQTS)

3) Brugada Syndrome

4) Wolff-Parkinson-White Syndrome (WPW)

Question 30

What are the most significant methods for differentiating anomalous coronary artery from other conditions?

Answer 30

Anomalous coronary artery has no murmur and the ECG tends to be normal.

Question 31

How does anomalous coronary arteries lead to sudden cardiac death in young patients?

Answer 31

External compression during exertion, leading to myocardial ischemia and lethal ventricular arrhythmias.

Question 32

What are the pertinent negatives seen with anomalous coronary artery origin?

Answer 32

No murmur or family history typically associated. ECG findings are often normal.

Question 33

How can you differentiate anomalous coronary artery from HCM?

Answer 33

Distinguished by a murmur that increases with Valsalva.

Question 34

What are the most reliable diagnostic tools for identifying anomalous coronary artery origin and what are their limitations?

Answer 34

Transthoracic echocardiography can sometimes detect coronary anomalies but this is often insufficient. CT coronary angiography and cardiac MRI are the gold standard methods for visualizing coronary artery anatomy and confirming the diagnosis.

Question 35

How can you differentiate anomalous coronary artery from Congenital Long QT Syndrome (LQTS) ?

Answer 35

Prolonged QTc (>450 ms in men, >470 ms in women) on ECG.

Question 36

How can you differentiate anomalous coronary artery from Brugada Syndrome?

Answer 36

Characteristic ST elevation in V1-V3.

Question 37

How can you differentiate anomalous coronary artery from Wolff-Parkinson-White Syndrome (WPW)?

Answer 37

Short PR interval with a delta wave and widened QRS complex.

WPW is not a major cause of SCD.

Question 38

What is the third most common cause for SCD in young adults?

Answer 38

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Question 39

What is the pathophysiology of Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) and how does it lead to sudden cardiac death in young patients?

Answer 39

ARVC is a non-ischemic autosomal dominant genetic disorder characterized by fibrofatty replacement of the myocardium, predominantly in the right ventricle. This weakens the right ventricular wall, leading to right ventricular dysfunction, reentrant ventricular arrhythmias, and sudden cardiac death, especially during physical exertion.

Question 40

What clinical clues suggest Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) in a young patient presenting with sudden cardiac death or exertional symptoms?

Answer 40

Clues include syncope, palpitations, or sudden collapse during exercise in a young individual. Common ECG findings include T-wave inversions in V1-V3 and epsilon waves (small deflections after the QRS complex).

Question 41

What are the primary risk factors for Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)?

Answer 41

Risk factors include a family history of sudden cardiac death, mutations in desmosomal proteins (e.g., plakoglobin, desmoplakin), and participation in high-intensity physical activity. It is more common in Southern European populations.

Question 42

What are the most reliable diagnostic tools for identifying Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) and what are their characteristic findings?

Answer 42

Diagnostic tools include ECG (showing T-wave inversions in V1-V3 and epsilon waves), cardiac MRI (revealing right ventricular dilation and fibrofatty infiltration), and genetic testing for mutations in desmosomal proteins. Biopsy may confirm fibrofatty changes, but it is rarely performed due to invasiveness.

Question 43

What conditions should be included in the differential diagnosis of sudden cardiac death in young athletes, and how can ARVC be differentiated?

Answer 43

Differential diagnoses include hypertrophic cardiomyopathy (HCM), long QT syndrome (LQTS), Brugada syndrome, and anomalous coronary arteries. ARVC is differentiated by its specific ECG findings (T-wave inversions in V1-V3, epsilon waves) and characteristic imaging findings on MRI.

Question 44

How can you differentiate Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) from hypertrophic cardiomyopathy, long QT syndrome, Brugada syndrome, and Wolff-Parkinson-White syndrome in a young patient presenting with sudden cardiac death?

Answer 44

ARVC: T-wave inversions in V1-V3, epsilon waves, right ventricular dilation on MRI. HCM: Systolic murmur that increases with Valsalva. LQTS: QTc >450 ms (men) or >470 ms (women). Brugada: ST elevation in V1-V3. Anomalous coronary arteries: No murmur, normal ECG.

Question 45

What is the pathophysiology of Long QT Syndrome (LQTS) and how does it predispose to sudden cardiac death?

Answer 45

LQTS is caused by mutations in cardiac ion channels (e.g., KCNQ1, KCNH2) that lead to delayed repolarization of the myocardium. This prolongs the QT interval on ECG, predisposing to polymorphic ventricular tachycardia, particularly torsades de pointes, which can degenerate into ventricular fibrillation and cause sudden cardiac death.

Question 46

What are the differences between Romano-Ward syndrome and Jervell and Lange-Nielsen syndrome in terms of inheritance, clinical features, and associated conditions?

Answer 46

Romano-Ward syndrome is an autosomal dominant form of LQTS with no extracardiac features. Jervell and Lange-Nielsen syndrome is autosomal recessive and associated with congenital sensorineural deafness. Both syndromes involve mutations in ion channel genes (e.g., KCNQ1, KCNE1).

Question 47

What clinical clues suggest Long QT Syndrome (LQTS) in a patient presenting with syncope or arrhythmias?

Answer 47

Clues include recurrent syncope, often triggered by exercise, emotional stress, or sudden loud noises. Family history of sudden cardiac death is common. Patients may report palpitations or have episodes of torsades de pointes.

Question 48

What are the ECG findings characteristic of Long QT Syndrome (LQTS) and how is the QTc interval calculated?

Answer 48

ECG findings include prolonged QTc interval (>450 ms in men, >470 ms in women), with a characteristic notched T wave in some cases. QTc is calculated as QT interval (ms) divided by the square root of the RR interval (seconds).

Question 49

What are the risk factors and triggers for torsades de pointes in patients with Long QT Syndrome?

Answer 49

Risk factors include electrolyte disturbances (e.g., hypokalemia, hypomagnesemia), medications that prolong the QT interval (e.g., antiarrhythmics, macrolides, antipsychotics), and genetic predisposition. Triggers include exercise, emotional stress, and loud noises.

Question 50

What is the management of Long QT Syndrome (LQTS) and how can torsades de pointes be treated in these patients?

Answer 50

Management includes beta-blockers (e.g., propranolol) to reduce adrenergic triggers, avoidance of QT-prolonging drugs, and electrolyte correction. High-risk patients may require an implantable cardioverter-defibrillator (ICD). Acute torsades is treated with IV magnesium sulfate and defibrillation if unstable.

Question 51

What drugs can cause torsades de pointes?

Answer 51

Macrolides, Fluoroquinolones, anti-psychs, tricyclic antidepressants (TCAs), SSRIs, methadone, oxycodone, antiarrhythmics (quinidine, dofetilide, sotalol).

Question 52

What electrolyte distrubtions can cause torsades de pointes?

Answer 52

hypocalcemia, hypokalemia, hypomagnesemia.

Question 53

What is the initial management for torsades de pointes?

Answer 53

IV magnesium if the patient is stable.
Unsynchronized cardioversion (defibrillation) if the patient is unstable.

Question 54

What is the pathophysiology of Brugada Syndrome and how does it predispose to sudden cardiac death?

Answer 54

Brugada Syndrome is an autosomal dominant genetic disorder caused by mutations in the SCN5A gene, which encodes the cardiac sodium channel. This leads to impaired sodium ion flow and altered cardiac action potential, particularly in the right ventricular outflow tract. The result is an increased risk of ventricular arrhythmias and sudden cardiac death, particularly during rest or sleep.

Question 55

What are the characteristic ECG findings in Brugada Syndrome and how do they correlate with clinical risk?

Answer 55

Characteristic ECG findings include coved-type ST-segment elevation in leads V1-V3, often followed by a negative T wave. Type 1 Brugada pattern is diagnostic, while Type 2 and Type 3 require further testing. These patterns correlate with the risk of ventricular arrhythmias and sudden death.

Question 56

What clinical clues suggest Brugada Syndrome in a patient presenting with syncope or sudden cardiac death?

Answer 56

Clues include recurrent syncope, nocturnal agonal respirations, or sudden cardiac death, particularly in middle-aged men of Southeast Asian descent. Events often occur during rest, sleep, or febrile illnesses. A family history of sudden cardiac death is common.

Question 57

What are the genetic and demographic risk factors associated with Brugada Syndrome?

Answer 57

Risk factors include male gender, Southeast Asian ancestry, SCN5A mutations, febrile states, and medications that unmask Brugada patterns (e.g., sodium channel blockers, tricyclic antidepressants, and certain anesthetics).

Question 58

What conditions should be included in the differential diagnosis of Brugada Syndrome, and how can it be differentiated from other causes of sudden cardiac death?

Answer 58

Differential diagnoses include arrhythmogenic right ventricular cardiomyopathy (ARVC), long QT syndrome (LQTS), and myocardial infarction. Brugada is distinguished by the absence of structural heart disease (seen in ARVC), lack of prolonged QTc (as in LQTS), and ST elevation limited to V1-V3 without reciprocal changes (unlike MI).

Question 59

What is the management of Brugada Syndrome and how is it tailored to prevent sudden cardiac death?

Answer 59

Management includes avoidance of triggers such as fever and medications that exacerbate Brugada patterns. High-risk patients (e.g., those with prior ventricular arrhythmias or syncope) may require an implantable cardioverter-defibrillator (ICD). Quinidine may be used in select cases to reduce arrhythmogenic risk.