Cardiac Damage Due to Electric Shock

Introduction:

Since the discovery of electricity in the mid-1800s, electrical injuries have become one of the commonest hazards at workplaces and homes. Even before the discovery of electricity, humans were exposed to electrical injuries through lightning. The injuries may range from mild burns to severe organ damage. Most of the injuries are mild and may not require medical consultation.

Heart damage due to electric shock is a life-threatening condition that requires immediate medical care. The commonest heart damage produced is arrhythmias (abnormal heart rhythm) and cardiac arrest. Electric shock interferes with the heart’s electrical impulse and impairs the pumping ability of the heart.

What Is the Pathophysiology Behind Electric Shock?

Electricity is measured in amperes. It is the flow of electrons through a potential gradient. This difference in potential represents the force of electrons. The pathological events due to electric current on the body are called electric shock. Direct or indirect mechanisms can cause electric injuries. Direct contact of electrical energy with the person on the ground potentially results in direct damage. This results in cell membrane damage, cellular depolarization, and electroporation (creating cell membrane pores).

The indirect injury occurs secondary to other traumas like mechanical trauma, burns due to flash produced from heat from the electrical arc, or flame from combustible materials.

The severity of the electrical injury depends on several factors, like the type of current, voltage, resistance to current, the path of current through the body, the duration of exposure, and the amount of energy delivered. Alternating current is more dangerous.

The current flow occurs from the entry point of the current source to the exit point (which is the point usually in contact with the ground) through the tissues of least resistance. The magnitude of electrical injury depends on the intensity of the current. The average internal resistance of the human body is 500 Ohms. Bone, skin, and fat have higher resistance, while blood vessels and nerves have the least resistance.

On pathologic examination, areas of band necrosis along the conduction system and focal degeneration of smooth muscle fiber are seen.

What Are the Cardiovascular Effects of Electric Shock?

The passage of electric current through the body follows the vascular axis, current flows through the tissues of least resistance. Whether the current passage is horizontal (hand to hand) or vertical (head to foot or hand to foot), cardiac injury occurs.

The major cardiac complications caused due to electric shock are:

1. Myocardial Injuries:

The direct effect of electric current results in cardiac damage. Electric shock cardiac damage may result in myocardial infarction (heart attack) or cardiac arrest. These are life-threatening conditions that need immediate medical care. Myocardial infarction occurs due to blockage of blood flow to the heart.

The different mechanisms which lead to myocardial infarction are the following:

• Generalized severe hypotension leads to a reduction in coronary blood flow.

• Coronary thrombosis.

• Injuries related to the release of catecholamine.

The diagnosis is challenging as chest pain is often absent, and ECG (Electrocardiogram) shows non-specific changes. In cases of coronary artery damage, classic clinical symptoms of myocardial infarction and ECG changes are present. Damage to the right coronary artery is more common as it is close to the chest wall.

2. Cardiac Arrhythmia:

Cardiac arrhythmia (abnormal heart rhythm) is the most common complication of cardiac electrical damage. The most common arrhythmias are sinus tachycardia and premature ventricular contraction. Exposure to direct current results in ventricular asystole. Ventricular fibrillation is more frequent with alternating current than with direct current. Most arrhythmias start immediately after exposure, but delayed ones are sometimes seen.

3. Other Cardiac Complications:

Conduction disturbances are other cardiac complications that occur due to cardiac electric shock damage. These include sinus bradycardia, atrioventricular block, and bundle-branch block. Sinoatrial and Atrioventricular nodes are most vulnerable to electrical injury.

Smaller vessels are more affected than large arteries because large arteries dissipate the heat produced due to electric current. Vascular injuries in the extremities may lead to compartment syndrome. Other cardiac complications caused are transient arterial hypertension, transient autonomic dysfunction, and hemorrhagic pericarditis (fluid and blood buildup of pericardium).

How Is the Condition Managed?

Before starting medical care, the first thing to do is to turn off the current source. After which symptomatic management is done. In the case of cardiac arrest victims, immediate resuscitation improves the prognosis. Head and neck immobilization should be done in all cases, even where spinal cord injury is not suspected. The patient should be admitted to specialized burn care units if extensive burn is present. Intravenous hydration is done to compensate for the fluid requirement. In patients who do not have extensive burns or other life-threatening injuries, ECG monitoring is done in intensive care units to assess arrhythmias.

The arrhythmia risk is lower for conscious patients with low voltage injuries and the absence of cardiac arrest and normal ECG. However, cardiac monitoring should be carried out in such patients if they have a known history of cardiac disease. Cardiac monitoring should be done for a minimum of 24 hour period. Electrical injury exposes victims with cardiac electronic devices to specific hazards. In patients with pacemakers, the electric noise leads to device inhibition.

In the case of pregnant women, there is an additional risk of fetal complications. Spontaneous abortion may occur as a result of electrical injuries.

Hospital administration with 24-hour cardiac monitoring is needed in the following cases of electrical injury:

• Unconscious patients with cardiac arrest.

• High voltage injury.

• Abnormal vital parameters.

• History of cardiorespiratory conditions.

• Pregnancy.

• Increase in troponin levels.

• Extensive burns or soft tissue damage.

• Abnormal ECG (Electrocardiogram).

Conclusion:

Cardiac damage due to electric shock is a life-threatening condition that requires immediate medical attention. The commonest heart damage produced is arrhythmias and myocardial injuries. Cardiac complications due to electrical injury are reversible in most cases but may sometimes have long-term complications.