John P. Cunha, DO, is a U.S. board-certified Emergency Medicine Physician. Dr. Cunha's educational background includes a BS in Biology from Rutgers, the State University of New Jersey, and a DO from the Kansas City University of Medicine and Biosciences in Kansas City, MO. He completed residency training in Emergency Medicine at Newark Beth Israel Medical Center in Newark, New Jersey.
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
I see a number of patients with
hyperthyroidism. Very frequently, their
symptoms involve the heart. The most
common symptoms are a feeling of palpitations and
a sensation of a racing heart beat. These symptoms are due to a physiologic
effect of thyroid hormone on the heart. I thought I'd take a moment to explain
more about what impact thyroid
hormone can have on the heart and why these symptoms result.
Many of the signs and symptoms
patients experience when they are diagnosed with hyperthyroidism result from the
direct effect of thyroid hormones on the heart.
While heart effects are also
seen in hypothyroidism, they are usually much more
obvious in hyperthyroidism.
Excess
thyroid hormone causes palpitations and some degree of exercise intolerance that
is due to an increased heart rate and fatigue.
Palpitations are unpleasant sensations of irregular and/or forceful beating of the heart. Some persons with palpitations have no heart disease or abnormal heart rhythms and the reasons for their palpitations are unknown. In others, palpitations result from
abnormal heart rhythms (arrhythmias).
Arrhythmias refer to heartbeats that are too slow, too rapid, irregular, or too early.
Rapid arrhythmias (greater than 100 beats per minute) are called tachycardias.
Slow arrhythmias (slower than 60 beats per minute) are called bradycardias.
Irregular heart rhythms are called fibrillations (as in
atrial fibrillation).
When a single heartbeat occurs earlier than normal, it is called a premature contraction, and this can cause the sensation of a forceful heartbeat.
Abnormalities in the atria, the ventricles, and the electrical conducting system [the Sino-atrial (SA) node, and the Atrio-ventricular (AV) node] of the heart can lead to arrhythmias that cause palpitations.
The atria (right atrium and left atrium) are the upper chambers of the heart.
The right atrium receives venous blood from the body and pumps it into the right ventricle.
The left atrium receives oxygenated blood from the lung and pumps it to the left ventricle.
The ventricles are lower chambers of the heart.
Each heart has two ventricles (right and left ventricles).
The right ventricle pumps venous blood to the lung and the left ventricle pumps oxygenated blood to the rest of the body.
The SA node is the pacemaker of the heart and is located in the right
atrium. The electrical signals initiated in the SA node are transmitted to
the atria and the ventricles to stimulate heart muscle contractions
(heartbeats). The AV node is specialized heart tissue which acts as an
electrical relay station between the atria and the ventricles. Electrical
signals from the SA node and the atria must pass through the AV node to
reach the ventricles.
When rapid arrhythmias (tachycardias) and premature contractions occur
because of abnormal electrical activity of the atria, they are called
atrial tachycardias and premature atrial contractions (PACs). When
tachycardias and premature contractions occur because of abnormal
electrical activity of the ventricles, they are called ventricular
tachycardias and premature ventricular contractions (PVCs).
Slow arrhythmias (bradycardias) can occur because of slowing of the
electrical signals initiated by the SA node, a condition called sinus
bradycardia. Bradycardias can also result from varying degrees of "heart
block," wherein certain medications or diseases in the electrical
conduction system of the heart impede the transmission of signals from
the atria to the ventricles (see the "Bradycardias" section
below).
Premature contractions are isolated heartbeats that occur earlier than
expected. The premature contraction is followed by a pause, as the heart
electrical system "resets" itself. The contraction following the
pause is usually more forceful than normal contractions. The patients
frequently perceive these more forceful contractions as palpitations.
Panic attacks are sudden feelings of terror that strike without warning. These episodes can occur at any time, even during sleep. A person experiencing a panic attack may believe that he or she is having a heart attack or that death is imminent. The fear and terror that a person experiences during a panic attack are not in proportion to the true situation and may be unrelated to what is happening around them. Most people with panic attacks experience several of the following symptoms: racing heartbeat, faintness, dizzyness, numbness or tingling in the hands and fingers, chills, chest pains, difficulty breathing, and a feeling of loss or control. There are several treatments for panic attacks.
An arrhythmia is an abnormal heart rhythm. With an arrhythmia, the heartbeats may be irregular or too slow (bradycardia), to rapid (tachycardia), or too early. When a single heartbeat occurs earlier than normal, it is called a prmature contraction.
Angina is chest pain that is due to an inadequate supply of oxygen to the heart muscle.
Angina can be caused by coronary artery disease or spasm of the coronary
arteries. EKG, exercise treadmill, stress echocardiography, stress thallium, and cardiac
catheterization are important tests used in the diagnosis of angina.
Heart attack happens when a blood clot completely obstructs a coronary
artery supplying blood to the heart muscle. A heart attack can cause chest pain, heart failure, and electrical
instability of the heart.
Hypoglycemia is a syndrome caused by low blood sugar. Symptoms of hypoglycemia include palpitations, trembling, intense hunger, sweating, nervousness, and weakness. Consuming lifesavers, table sugar, soda, and juice are good treatment options for hypoglycemia.
Mitral valve prolapse (MVP) is also also known as "click murmur syndrome" and "Barlow's syndrome." Mitral valve prolapse is the most common heart valve abnormality. Signs and symptoms of mitral valve prolapse include: fatigue, palpitations, chest pain, anxiety, and migraine headaches. Echocardiography is the most useful test for mitral valve prolapse. Most patients do not need any treatment, however, patients with severe prolapse may need treatment.
Potassium is an essential electrolyte necessary for cell function. Low potassium (hypokalemia) may be caused by diarrhea, vomiting, ileostomy, colon polyps, laxative use, diuretics, elevated corticosteroid levels, renal artery stenosis, and renal tubular acidosis, or other medications. Symptoms of low potassium include weakness, aches, and cramps of the muscles. Treatment is dependant upon the cause of the low potassium (hypokalemia).
Premature ventricular contractions (PVCs) are premature heartbeats originating from the ventricles of the heart. PVCs are premature because they occur before the regular heartbeat. There are many causes of premature ventricular contractions to include: heart attack, high blood pressure, congestive heart failure, mitral valve prolapse, hypokalemia, hypoxia, medications, excess caffeine, drug abuse, and myocarditis.
Marfan syndrome is hereditary condition affecting connective tissue. A person with Marfan syndrome may exhibit the following symptoms and characteristics: dislocation of one or both lenses of the eye; a protruding or indented breastbone; scoliosis; flat feet; aortic dilatation; dural ectasia; stretch marks; hernia; and lung collapse. Though there is no cure for Marfan syndrome, there are treatments that can minimize and sometimes prevent some complications.
Heart rhythm disorders vary from minor palpitations, premature atrial contractions (PACs), premature ventricular contractions (PVCs), sinus tachycardia, and sinus brachycardia, to abnormal heart rhythms such as tachycardia, ventricular fibrillation, ventricular flutter, atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), Wolf-White-Parkinson syndrome, brachycardia, or heart blocks. Treatment is dependant upon the type of heart rhythm disorder.
Aortic valve stenosis is an abnormal narrowing of the aortic valve of the heart. The causes of aortic stenosis are wear and tear of the valve in the elderly, congenital, or scarring or scarring of the aortic valve from rheumatic fever. Symptoms include angina, fainting, and shortness of breath. Treatment is dependant upon the severity of the condition.
Heart valve disease occurs when the heart valves do not work the way they should. Symptoms of valve disease include shortness of breath, weakness or dizziness, discomfort in your chest, palpitations, swelling of your ankles, feet or abdomen, and rapid weight gain.
A heart murmur is the sound generated when blood flow within the heart is not smooth. Causes of heart murmurs can be functional, congenital, or caused heart valve conditions. Symptoms of a heart murmur may be none, or may include chest pain, shortness of breath, and arm, leg, and ankle swelling. Treatment of a heart murmur depends on the cause.
Wolff-Parkinson-White syndrome is a condition in which abnormal electrical pathways in the heart cause arrhythmias. Symptoms of Wolff-Parkinson-White syndrome include tachycardia, dizziness, palpitations, fainting, and shortness of breath. Wolff-Parkinson-White syndrome is a common cause of paroxysmal supraventricular tachycardia. Wolff-Parkinson-White syndrome is caused by mutations in the PRKAG2 gene.
Ticks are known transmitters of disease to humans and animals. Tick-borne diseases include Lyme disease, Rocky Mountain spotted fever, Q fever, tularemia, babesiosis, and Southern tick-associated rash illness. Infected ticks spread disease once they've bitten a host, allowing the pathogens in their saliva and mouth get into the host's skin and blood. Tick bites are typically painless, but the site of the bite may later itch, burn, turn red, and feel painful. Individuals allergic to tick bites may develop a rash, swelling, shortness of breath, numbness, or paralysis. Tick bite treatment involves cleaning and applying antibiotic cream.
Paroxysmal supraventricular tachycardia (PSVT) is an abnormal conduction of electricity in particular areas of the heart. PSVT was referred to at one time as paroxysmal atrial tachycardia or PAT, however, the term PAT is reserved for as specific heart condition. Symptoms of PSVT include weakness, shortness of breath, chest pressure, lightheadedness, and palpitations. PSVT is treated with medications or procedures that return the heart to its normal electrical pattern.
Heart failure is caused by many conditions including coronary artery disease, heart attack, cardiomyopathy, and conditions that overwork the heart. Symptoms of heart failure include congested lungs, fluid and water retention, dizziness, fatigue and weakness, and rapid or irregular heartbeats.
Chagas disease is an infection caused by the T. cruzi parasite. Symptoms of Chagas disease include rash, swollen lymph nodes, fever, fatigue, nausea, vomiting, and the Romaña sign. An ELISA test is used to diagnose Chagas disease. Treatment depends upon the phase of the disease and the patient's age.
Schistosomiasis (snail fever), a disease caused by parasites, causes a variety of symptoms and signs, such as cough, rash and bloody diarrhea. Praziquantel is used in the treatment of schistosomiasis.
Dilated Cardiomyopathy is a condition where the heart's ability to pump blood is decreased because the heart's main pumping chamber is enlarged and weakened. Symptoms of dilated cardiomyopathy include chest pain, heart failure, swelling of the lower extremities, fatigue, weight gain, fainting, palpitations, dizziness and blood clots.
Hypertrophic cardiomyopathy (HCM) affects many people today. Many people with HCM have no symptoms or only minor symptoms, and live a normal life. Other people develop symptoms, which progress and worsen as heart function worsens.
Restrictive cardiomyopathy, the rarest form of cardiomyopathy, is a condition in which the walls of the lower chambers of the heart (the ventricles) are abnormally rigid and lack the flexibility to expand as the ventricles fill with blood.
The pumping or systolic function of the ventricle may be normal but the diastolic function (the ability of the heart to fill with blood) is abnormal. Therefore, it is harder for the ventricles to fill with blood, and with time, the heart loses the ability to pump blood properly, leading to heart failure.
The heart is a two stage electric pump whose job it is to circulate blood through the body. There is a group of cells that serve as an automatic pacemaker located in the atrium that generates an electrical current that spreads to the heart muscle cells to generate a coordinated squeeze, so that the pump can function.
The heart has four chambers, the right and left atria (singular= atrium) and
the right and left ventricles. The right side of the heart pumps blood to the
lungs while the left side pumps it to the rest of the body.
Blood from the body is collected in the right atrium and is pushed into the
right ventricle with a small beat of the upper chamber of the heart. The right
ventricle then pumps the blood to the lungs to pick up oxygen. They oxygen-rich
blood returns to the left atrium where the small atrial beat
pushes it to the left ventricle. The left ventricle is much thicker than the
right because it needs t...
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