How does lightning affect the heart?

How does lightning affect the heart?

Lightning is a fearful natural phenomenon which can cause fatal injuries. But only 10% of the victims die immediately and 90% survive, sometimes with severe and permanent disabilities. Various complications in relation to the heart and blood vessels, associated with lightning injury has been described. Various ECG changes and heart rhythm abnormalities which could even be fatal have been noted in lightning strikes.

Heart muscle may show bruising or damage leading to heart failure. One important type of heart muscle damage is similar to that seen in stress cardiomyopathy with enlargement of the lower portion of the left ventricle. Left ventricle is the lower muscular chamber of the heart. Stress cardiomyopathy is heart muscle damage due to severe emotional stress like bereavement, typically loss of spouse in an elderly female. Hence that type of heart muscle disease has also been called broken heart syndrome.

Mechanisms proposed for the injury to heart include direct damage by the heat, surge in stress related hormones, localized contraction of the muscles of the blood vessel wall (coronary artery spasm), and generalized injury to the blood vessels of the heart. Fluid collection in the lungs causing breathlessness can occur due to heart failure. Damage to muscles elsewhere could lead to kidney failure and retention of fluids in the body. This generalized fluid overload can also cause collection of fluid in the lungs (pulmonary edema).

Injuries to the covering of the heart (pericardium) with collection of fluid inside it can occur, surrounding the heart. Injury can also occur to the major blood vessel known as aorta which carries oxygenated blood to the whole body. A tear in inner lining of the aorta known as aortic dissection can be a life-threatening complication of aortic injury.

Abnormal function of cardiac implantable electronic devices (CIED) can occur in some cases. These are pacemakers, implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT) or heart failure device. They are used for the treatment of heart rhythm disorders and heart failure. An ICD can be life-saving in a lightning strike as it can automatically treat lethal heart rhythm disorders caused by lightning. Occasionally the electrical signals from lightning may also interfere with the function of the ICD and cause an unwanted ICD shock.

Lightning strikes occur when the potential difference between the clouds and ground objects is greater than 30,000 Volts so that they can overcome the electrical resistance of the atmospheric air. The currents generated range from 30,000 to 100,000 Amperes and last from 0.001 to 0.1 seconds. It is estimated that 1.4 billion lightning flashes occur in a year globally as per satellite data.