What are the signs and symptoms of heart rhythm disorders?
Many people may have heart rhythm disturbances and never be aware of them. Premature atrial contractions (PACs) and premature ventricular contractions (PVCs) are variations of normal and most often, people are unaware that an extra beat has occurred. However, some patients are keenly aware of any extra heartbeat, even if it is a normal variant and requires no treatment.
That said, the initial symptom of dysrhythmia is often palpitations, a sensation that the heart is beating too quickly, too slowly, beating irregularly, or skipping a beat. The palpitations may be intermittent or may require medical intervention to resolve.
Because of the heart rhythm abnormality, other symptoms may occur because of decreased cardiac output (the amount of blood that the heart pushes out to meet the body's demand for oxygen and energy). The patient may complain of lightheadedness, weakness, nausea and vomiting, chest pain, and shortness of breath.
In critical situations, the patient may fall to the ground or lose consciousness. This may be due to life-threatening dysrhythmias like ventricular fibrillation or ventricular tachycardia. It may be due to heart rates so fast that there isn't enough blood pressure generated to supply the brain with what it needs. The same result can also occur if the heart beats too slowly and insufficient blood pressure is generated.
What are the different types of heart rhythm disorders?
Heart rhythm disorders are classified according to where they occur in the heart and how they affect the heartbeat.
Premature atrial contractions (PACs) and premature ventricular contractions (PVCs)
Every person experiences the occasional palpitation in which the atrium or the ventricle beats early. These premature atrial contractions (PACs) or premature ventricular contractions (PVCs) are normal variants and most people are unaware of their occurrence. However, some patients report a palpitation in the chest and neck, often described as a "thump" or "thud." PACs and PVCs in otherwise healthy individuals do not pose any health risks.
The heart, its cells, and its electricity may come under many outside influences that may cause it to beat more quickly. Sinus tachycardia (sinus = from the SA node + tachy = rapid + cardia = heart), or a rapid regular heartbeat, is a common rhythm issue. It occurs when the body signals the heart to pump more blood, or when the electrical system is stimulated by chemicals.
The body needs increased cardiac output in times of physiologic stress. Cardiac output is the amount of blood the heart pumps in the course of 1 minute. It can be calculated by the amount of blood that the heart pumps with each beat (stroke volume) multiplied by the heart rate.
Cardiac output = (stroke volume) x (heart rate)
The stroke volume tends to be relatively constant. When the body requires extra oxygen delivery, the heart rate needs to increase to meet that demand. Examples include:
exercise, in which the muscles have greater oxygen requirements and the heart rate speeds up to pump more blood to meet that need;
dehydration, in which there is less fluid in the body and the heart rate has to speed up to compensate; or
in cases of acute bleeding that may occur after trauma.
The electrical system can be stimulated in a variety of ways to make the heart beat faster. In times of stress, the body generates cortisol and adrenaline, causing an increased heart rate in addition to other changes in the body. Think of being frightened and feeling your heart race. Increased thyroid hormone levels in the body can also cause a tachycardia. Ingestion of a variety of drugs can also cause the heart to race, including caffeine, alcohol, and over-the-counter cold medications that include chemicals such as phenylephrine and pseudoephedrine. These compounds are metabolized by the body and act like an adrenaline stimulus to the heart. Illegal drugs such as methamphetamine and cocaine can also cause a sinus tachycardia.