Prashant Tamang, the winner of Indian Idol Season 3, who rediscovered himself as an actor in Paatal Lok 2, has died of a sudden cardiac arrest, when the heart stops abruptly, at 43. Although he reportedly slept comfortably, he did not wake up in the morning. His family rushed him to the hospital where he was declared dead on arrival.Sudden cardiac arrest during sleep is least understood. “But it is quite common. Apparently healthy people go to bed normally never to wake up again. Most of them are unaware of their underlying heart condition, which can trigger a sudden cardiac arrest,” says Dr Ranjan Shetty, lead cardiologist and medical director, Sparsh Hospital, Bengaluru.Why does sudden cardiac arrest take place at night?This is because at night, the body shifts into a restful mode, what we call a parasympathetic response. “The heart rate slows down. Each time your heart beats, electrical signals travel through it. Now, there could be changes to this pattern during sleep which can cause much faster or slower heartbeats. Sometimes this leads to severe irregular heartbeats or arrhythmia, which can lead to sudden stoppage of the heart. In people with underlying heart rhythm disorders, therefore, the risk increases between midnight to early morning,” says Dr Shetty.Also read | Fund manager, 47, dies of sudden cardiac arrest while on holiday: How young Indians can get a simple test and prevent this silent heart riskWhy snoring bouts and sleep apnea increases risk of sudden cardiac arrest at night?Sleep apnea, a sleep disorder where breathing intermittently stops and resumes, leads to falls in oxygen levels. “This stresses out the heart and its rhythms become unstable, triggering sudden cardiac arrest during sleep. Many people snore and do not even know that they have undiagnosed sleep apnea,” explains Dr Shetty.Silent heart attack at nightA plaque may not be stable and may even seem non-threatening on its own. But hormonal shifts in the early morning hours naturally increase blood pressure and heart rate, stressing the heart out and potentially triggering plaque rupture. “Unstable plaque causes sudden cardiac arrest during sleep as it ruptures, forming a blood clot that abruptly blocks a coronary artery, cutting off oxygen to the heart muscle, triggering a fatal arrhythmia and leading to stoppage,” says Dr Shetty. None of these changes are felt by the patient as they are in deep sleep.Is electrolyte imbalance to blame?Low potassium or magnesium (due to dehydration, alcohol, diuretics) can trigger fatal arrhythmias, especially during sleep. “That’s why alcohol before sleep is not recommended at all because of its disruptive potential,” says Dr Shetty.More co-morbidities by age 40A stressful lifestyle means by age 40, most young Indians have high cholesterol, blood pressure or diabetes. “All of these lie silent without regular checkups until a sudden fatal rhythm occurs. The worst is stress induced by long working and sedentary hours, poor sleep, career anxiety and financial challenges. “All of these raise stress hormones like cortisol and adrenaline and in turn trigger dangerous heart rhythms. Even without blockages, stress can flip the switch and trigger sudden cardiac arrest. In fact, belly fat, fatty liver, insulin resistance and inflammation act as risk accelerators. That’s why heart care begins by keeping all these parameters within range,” says Dr Shetty.Story continues below this adAlso read | As sudden cardiac arrests become common in young people, experts urge the need for these medical tests before starting gymHow to reduce risk in your 40sDr Shetty advises basic tests like lipid profile, blood sugar, blood pressure, stress test (this is a must for those with a family history), electrocardiogram and echocardiogram to understand the heart’s underlying issues and electrical activity. “If there is anything unusual, the doctor will do a cardiac holter test, which is a portable ECG worn for 24-48 hours, to capture arrhythmias during daily activities. Cardiac event monitors, which are worn for longer periods, record events when you press a button whenever you feel uneasy. The patterns give a good idea about how risky your arrhythmia might be and that can be corrected with medication,” says Dr Shetty.