Sudden cardiac arrest…sounds a lot like a heart attack, right? But it’s like the difference between wiring and plumbing. You might say Michael Jackson’s death has put the spotlight on cardiac arrest, a condition quite different from a heart attack, and on various other electrical aspects of the heart.
Illustration: Jayachandran / Mint
A heart attack is more of a plumbing failure, usually brought on by blockages in the coronary artery, which stop blood supply to the heart. The heart is made primarily of specialized cardiac muscle tissue. When the blood supply stops, the heart muscle it supplies dies and the patient suffers a heart attack.
Cardiac arrest is more like a short-circuiting or electrical failure in the cardiac system. When the electrical signals in our nerves controlling the timing and organization of heartbeats become chaotic, the heart stops beating, leading to sudden death as the brain is starved of oxygen. There are a bunch of triggers that could disrupt this normally rhythmic electrical pulse—from a viral fever to imbibing a cocktail of painkillers and drugs.
In medical circles, cardiologists are jokingly divided into two sets: the plumbers and electricians. The former mind the network of arteries and fix the blocks and leaks: They put in stents, re-route blood supply by sewing in new pipes in what is called bypass surgery. The latter attend to the network of electrical circuitry wiring the heart and can sometimes set that rhythm right when it falters.
Could your heart stop suddenly?
Most of us are well aware of the risks of heart attacks and blocked arteries, and are aware that Indians are especially prone to Metabolic Syndrome, which heightens risk. However, the risk of dying of a heart attack is far less than of sudden cardiac arrest (SCA): Doctors say that there is only a 7-minute window to save the life of a victim of cardiac arrest; heart attacks can give you as much as 20 minutes to prevent damage and rescue is often possible well after that, with little damage.
The American Heart Association estimates that at least 95% of cardiac arrest victims die before reaching hospital. In India, about 500,000 people die of SCA every year, according to pacemaker manufacturer Medtronic India —doctors agree and add that most of these deaths could have been prevented.
SCA often seems to happen to people with no known health problems. But the truth is they do have a problem; they just don’t know about it .
Also Read Is your heart at risk?
The wiring of your heart
Most cardiac arrests that lead to death are caused by abnormal heart rhythms. It can occur when the heart beats too quickly or when the heartbeat becomes chaotic (fibrillation). Sometimes, the irregular heartbeat (known as arrhythmia) can become a failure of rhythm, a cardiac “arrest”.
The root of the problem is in the wiring of the heart, when the cable supply of nerves conduct impulses badly or misfire. A.B. Mehta, professor of cardiology, Mumbai University, and director of cardiology, Jaslok Hospital, Mumbai, explains that ventricular defibrillation—when nerve signals in the lower chamber of the heart (the ventricle) are jammed —leads to a higher incidence of cardiac arrest. “If the heart is studied electrophysiologically, then this can be spotted and action taken to prevent cardiac arrest,” he says.
Who is at risk?
All those who have had a heart attack or have a history of heart disease are at risk of sudden cardiac arrest.
Doctors in India say that with the alarming increase in prevalence of coronary artery disease (CAD), diabetes and hypertension, the incidence of SCA is also on the rise, especially in urban regions. In fact, 80% of pacemaker and ICD devices are implanted in those who have a history of myocardial infarction (heart attack or blockages in the artery).
According to Balbir Singh, senior consultant, interventional cardiology and electrophysiology, Indraprastha Apollo Hospitals, New Delhi, three groups are greatly at risk:
• Those with prior history of a heart attack.
• Those with cardiac myopathy (inflammation of the heart muscle, which can be triggered by causes as varied as a viral fever or drug/alcohol use).
• Those who are genetically prone.
Symptoms to look out for: “Multiple missing bits” such as irregular pulse, irritability of the heart, missing beats. Unexplained syncopes (fainting spells, see ‘Surf’), often misdiagnosed as epileptic attacks, could also be early warning symptoms.
Tests to take: Electrocardiogram (ECG), 2-D echo and 24-hour Holter monitoring can give doctors an inkling as to whether the heart may trip up or not. Vanita Arora, senior consultant electrophysiologist, Indraprastha Apollo Hospitals, New Delhi , says: “A family history of sudden cardiac death should also be a marker for being alert.”
Fixing the fault
It is to address ventricular arrhythmia (which affects the ventricles, the lower chambers of the heart, and which is more likely to lead to cardiac arrest) that electrical cardiac devices such as pacemakers come into play. As Dr Arora explains, when your power supply is erratic, you invest in a back-up such as a genset or inverter.
Not all cases of arrhythmia need such a back-up. Electrophysiologists can fix some types with a surgical procedure called radio frequency ablation. Where devices are required, they assess the risks and requirements to determine whether a pacemaker or an implantable cardioverter defibrillator (ICD) or a combination device is needed. Placed under the skin of your chest or abdomen, these devices use electrical pulses to prompt the heart to beat at a normal rate. (Also see ‘Know’).
Too few devices, doctors?
Manufacturers of these devices point out that 18,000 pacemakers and ICDs were implanted in Indian hearts last year, compared with at least 150,000 stents (though this is perhaps an apples to oranges comparison). What is important is, says K.K. Sethi, director, cardiology, Heart and Lung Institute, New Delhi, is that “in India, about 80% of the people who need these devices (pacemakers and ICDs) do not get them, especially those outside the metro cities.” He says the issue “requires a change in mindset and rise in awareness”.
Dr Mehta says electrophysiology is still a nascent field in India. “There are very few EPs in India. The reason for that is (that) this is (a) comparatively new field. The procedures are very time-consuming. Being comparatively new, it is an expensive field too and less people have opted to take it as a speciality—though their numbers are steadily growing,” he says.
The plumbers and the electricians
Balbir Singh, senior consultant, interventional cardiology and electrophysiology, Indraprastha Apollo Hospitals, New Delhi, points out that not all electrical faults in the heart are as final as cardiac arrest. There are “common garden variety” heart ailments such as palpitations, he notes, which can be cured permanently by a simple semi-invasive procedure called radio frequency ablation.
Essentially, what happens in these cases is that some of the cells in the heart show altered electrical properties. Radio frequency energy is used to fix these cells. “First, we map the area of the heart to locate the abnormal electrical activity and then a catheter is guided to the offending tissue and radio frequency energy is passed,” explains Vanita Arora, senior consultant, electrophysiology, Indraprastha Apollo Hospitals, New Delhi.
“Whenever ventricular function is normal, then the preferred line of treatment is ablations,” says Dr Singh. However, he says that this form of treatment is often ignored by general practitioner, or GPs, and cardiologists, who prefer to put palpitation patients on life-long medicines, thereby creating new problems. “Many of these drugs have serious side effects. So yes, we (electrophysiologists) would like to spread awareness that there are cures for such…tachycardia (rapid heartbeat or palpitations) which should be explored.” As Dr Arora says: “In India, the preventive focus has largely been on heart attacks. We only know bypass and angioplasty as the ‘be all and end all’ of heart treatment.”
For more serious heart rhythm disorders such as complex arrhythmia (where the rhythm doesn’t just falter, but keeps altering) and atrial fibrillation (abnormal rhythm originating in the upper chambers of the heart), too, ablations could work, but Dr Singh says there are very few centres in India for the procedure.
However, it’s when the ventricular function that cardiac devices come into play. Sudden cardiac arrest is usually an outcome of ventricular arrhythmia.
Know more about implanted cardiac devices
Some issues with implanted cardiac devices (such as pacemakers, implantable cardioverter defibrillators and combos) used to trouble potential users: You can’t get an MRI, need to be careful of magnetic fields (security checks, cellphones) and the possibility of product recall (meaning a second surgery). Newer products address some of these concerns. US-based Medtronic launched the MRI-compatible EnRhythm MRI SureScan Pacing System in March. German firm Biotronik married telecom and Internet in its Home Monitoring System launched in India in May—from it, heart function data (akin to ECG) is wirelessly transmitted over a GPRS network to Biotronik’s service centre in Germany. Any anomaly or cardiac incident sends a red alert (SMS, email or fax) to the patient’s physician. The device works wherever there is a cellphone network.
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