Sudden Cardiac Death!!

 "Phidippides (490 BC) A Greek soldier and conditioned runner, Phidippides ran from Marathon to Athens to announce military victory over Persia. He delivered his message, then collapsed and died."

Several times we read news that an apparently healthy child/adult playing, collapses and dies suddenly!!

Two questions that immediately crop up in our minds are :

1. Can we identify who is at risk?
2. Can we prevent it from happening?

Let's first define Sudden Cardiac Death : "Natural death from cardiac causes, heralded by sudden onset loss of consciousness within 1 hour of onset of symptoms"

Young athletes, regarded as a special part of society, having unique lifestyle, capable of admirable and extraordinary physical achievements may harbor potentially lethal heart disease / susceptible to sudden death under a variety of circumstances.
SCD in athletes, although a rare event, have considerable emotional and social impact that goes beyond sport
• Although precise data of prevalence limited, overall risk low
• A 12 year survey from Minnesota : 1 in 200 000 / year
N Engl J Med 2003;349:1064-75
• A prospective population based study in Veneto region of Italy : 3 / 100 000 athletes per year
• The magnitude of this public health problem may be considerably underestimated because of 3 reasons :
 No systematic National registry; data mostly derived from high profile events or deaths of prolific athletes
 Expert cardiac pathologist rarely responsible for conducting postmortem examination
 Death from ion channelopathies or accessory pathways not identified during postmortem examination
 In India accurate data are not available but recently media attention was focused on a
Brazilian soccer player who died while playing for his adopted club
• In autopsy data the following were the most common causes for sudden cardiac death in athelets:
• Age < 35 years : HOCM (hypertrophic obstructive cardiomyopathy)– 36% Coronary artery abnormalities – 17% Myocarditis – 6% ARVD ( arryrhmogenic right ventricular cardiomyopahty)– 4% • Age > 35 years : CAD ( coronary artery disease)
• Other cardiovascular diseases accounted for 5% or less of these deaths in athletes
Sudden cardiac death in structurally normal heart:
• Long QT syndrome/ Short QT syndrome
• Brugada syndrome
• Wolff–Parkinson–White syndrome
• Catecholaminergic polymorphic tachycardia
• Coronary vasospasms
• Commotio cordis
• Drugs (amphetamine or cocaine)
Causes of sudden cardiac death in young athelets
Hypertrophic cardiomyopathy (HOCM)
(Cardiomyopathy refers to diseases of heart muscles).
• Principal cause of SCD on the athletic field in US (0.2 %; 1:500 in general population)
• The heart is thickened. The cardiac musles are disorganized. There is typical obstruction to left ventricular outflow during ejection of blood. Predominantly left ventricle is affected ( the chamber which pumps blood to entire body).There is increased electrical instability in heart. Dynamic left ventricle outflow obstruction at rest or with exercise is demonstrable in most patients
• Sudden death in HCM is probably a consequence of an electrically unstable and unpredictable myocardial substrate with reentrant ventricular tachyarrhythmias.

• In the future, genetic testing may be of value, but at the current time, the sensitivity of genetic testing for HCM is only 50%
• Five established risk factors for SCD in HCM are:
 History of recurrent syncope (unconsciousness)
 Family history of SCD
 Severe LV hypertrophy defined as maximum wall thickness >30mm
 Abnormal blood pressure response to exercise in patients younger than 40 years with a failure of the systolic blood pressure to increase by more than 25 mm Hg or a fall from peak blood pressure by more than 15 mm Hg, and
 Nonsustained ventricular tachycardia.

Implantable internal cardioverter (ICD) is indicated in patients of HCM with high risk features. ICD is implanted subcutaneously, similar to pacemaker. When ever it senses electrical disturbance in heart it internally delivers an electric shock. This electric shock restores the normal electric current system in heart. It is a very powerful tool for prevention of sudden cardiac death

ARVD ( Arrythmogenic Right Ventricular Dysfunction)
Another disease affecting heart muscle. In this case the defectives muscles are located in right ventricle (the chamber which pumps blood to the lungs)

 Cited as a major cause of sudden death in young people and athletes, particularly in the northeastern (Veneto) region of Italy (25% of sudden death in young athletes)
 less common in the U.S (4%)
 Characterized by loss of myocytes in the right ventricular myocardium with replacement by fat cells → segmental or diffuse wall thinning
 Clinical diagnosis challenging, but relies largely on familial occurrence, VT (ventricular tachyarrthymia- a serious electric current disturbance of heart which is fatal if not corrected immediately) , T-wave inversion in anterior leads of ECG and presence of epsilon waves in ECG.
 Echo, MRI shows - RV dilatation and/or segmental abnormalities in contraction of RV, aneurysm (localized dilatation), and deposition of fat cells in RV wall.

 Sudden death during exercise likely related to hemodynamic factors, ↑ sympathetic tone ( nervous system which mediated normal response to exercise) that culminate in VT

Myocarditis
 Myocarditis is an inflammatory disease of myocardium and a cause of sudden death in young athletes
 Usually of infectious etiology due to a variety of viral agents - enterovirus (e.g., Coxsackie virus), adenovirus, or parvovirus in young people, but also by drugs and toxic agents such as cocaine
 Myocarditis has different stages - active, healing, and healed pathologic stages.
 Due to this inflammation there is electrical imbalance in heart this leads to increased risk of VT.

Marfan syndrome
• Caused by gene mutation in fibrillin-1 (FBN1) gene.
• Prevalence of 1:5,000 to 1:10,000 in the general population
• Characterized clinically by a involvement of connective tissues in various parts of body-eyes, bones, heart and vessels.
• Cardiovascular manifestations are:
 There is dilatation of Aorta beyond its normal limits. Aorta is the biggest artery of body, which serves to supply blood to whole body including heart itself. Excessive dilatation causes stretching of the walls of aorta which predisposes it to dissection and rupture. Aortic rupture is instantaneously fatal. Aortic dissection carries a very high mortality if not detected and treated immediately. Weight lifting is a typical risk factor for aorta to dissect in patients with Marfan Syndrome. Patients with Marfan Syndrome should avoid lifting heavy weight.
 Heart valves are also affected in Marfan syndrome. There is increased tendency for left heart valve to leak which predisposes to VT and sudden death.
 Risk for aortic rupture usually linked to marked enlargement of the aorta (transverse dimension > 50 mm), although dissection (tear in wall of aorta) can occur with a normal (or near-normal) aortic root dimension.

Ehler Danlos Syndrome
• Rare genetic defect of connective tissue
• Carries a substantial risk of rupture of the aorta and its major branches
• Variable joint hypermobility, susceptibility to bruising, difficult wound healing, and often prematurely aged appearance.
Congenital anomalous coronaries
 Coronary arteries are the blood vessels which supply blood to heart.
 Anomalous coronaries refers to abnormal origin and course of coronary arteries.
 In some of these cases the left main coronary passes between aorta and pulmonary artery and it gets compressed during exercise this causes SCD.
 10-19% sports related deaths in athletes
 1.2% of non-sports related deaths in young individuals (14-40 yrs).
 Second most common cardiovascular cause of sudden death in young athletes

ATHEROSCLEROTIC CORONARY ARTERY DISEASE
Most frequent cause of these exercise-related cardiac events in adults >35 years of age
Both plaque rupture and possibly plaque erosion have been implicated as the immediate cause of exercise-related events in adults, although plaque rupture is more frequent
Frequently occur in coronary arteries that were not previously critically narrowed

Burke AP et al. Plaque rupture and sudden death related to exertion in men with coronary artery disease. JAMA 1999;281:921– 6.

Long QT Syndrome and Short QT Syndrome
This is one of the group of diseases which affect the ion channel transport across cell membrane of heart.
The current system flows in an organised fashion in cells of heart.
Ion channel diorders affects the flow of this current and predisposes to electrical instability in the heart, leading to serious VT.
On ECG it is manifestaed as lenghtening of QT interval (called as long QT syndrome) or shortening of QT interval called as Short QT syndrome LQTS or SQTS

 Different subtypes of LQTS exist depending upon the ion channel affected (sodium, potassium or calcium channels)
 Physical exertion (particularly swimming) appears to be a common trigger for ventricular arrhythmias in LQT1 ( this may explain some of the SCD in trained swimmers)
 LQT2 - more at-risk to auditory/emotional trigger (sometimes a sudden scream can precipitate VT in suceptible patients). This is also the scientific expalanation for the traditional hindi movie scenes in which emotions causes sudden death.
 LQT3 - at greater risk during rest and inactivity

CATECHOLAMINERGIC POLYMORPHIC VT (CPVT)
Genetic defect invloving Ryanodine receptor.
Predisposes to serious VT which are typically precipitated by exertion.

BRUGADA SYNDROME (BrS)

Gene mutation affecting cardiac sodium channel.
Causes sudden unexpained death during SLEEP
Charatertic ECG signs are present which manifest either at rest or on drug provocation.
ICD is the only treatment avalable.
Athletic-field risks unrelated to cardiovascular disease
Commotio cordis
 In the presence of structurally normal heart severe non penetrating injury to chest wall during sports can cause SCD known as commotio cordis
 Mechanism in by VT

High-velocity blows to the neck
Blows to the neck with Ice hockey puck can trigger arterial rupture and subarachnoid hemorrhage

How to prevent this from occuring

Proper screening of the subject who are taking part in competitive sports is effective way of predicting and reducing the risk. The preparticipation screening has been implemented in several countries and shown to be effective.

Pre-Participation Screening

 Sharp decline of mortality rates after the introduction of the nationwide screening program in Italy.
 Annual incidence of SCD in athletes ↓ by 89%, from 3.6/100,000 athlete/years in the pre-screening period (1979 to 1981) to 0.4/100,000 athlete-years in the late-screening period (1993 to 2004).
 Whether the result of the Italian study is applicable to other countries is of course, questionable
 In the US, currently there is no advocacy for routine ECG's, and the diagnostic tool used most frequently is a detailed history and physical examination
 With regard to India and other developing countries, such preparticipation screening will need enormous increase in the Government's commitment to public health given the huge population of people that needs to be screened and the low incidence of disease that cause sudden death.
 If preparticipation screening is far away in a country like India, the least we can do is provide external defibrillators in as many athletic events as possible, and train paramedics to use them properly.

Conclusion
Sudden cardiac death in athlete is rare.
If proper screening is conducted it is preventable.
May be in future we could develop blood test which could identify the genetic predisposition in a better way. Still our understanding of genetic causes of these diseases is limited and future of these diseases lies in genetics.
Probably now you would not be much surprised by reading the news in newspaper that an apparently healthy child while playing in school collapses and dies.