Encyclopedia of Health and Medicine

94 The Cardiovascular System
when the heart feels as if it were pounding, and
right before falling asleep at night.
SUBSTANCES THAT CAN CAUSE PALPITATIONS
albuterol
ALCOHOL
CAFFEINE
COCAINE
levothyroxine
ma huang
NICOTINE (tobacco)
pseudoephedrine
theophylline
The most common presentation of palpitations
is the premature beat, which can be atrial or ventricular
and feels like a skipped beat though it is
not. Because the premature beat is early, there is a
slight pause before the regular beat which makes
the regular beat feel enhanced. Such palpitations
are nearly always the result of stimulants (including
cold and flu preparations) or anxiety, and go
away either when the stopping the stimulant or
removing the cause of stress.
Palpitations require a doctor’s evaluation when
they occur
• frequently or for sustained periods of time
• with syncope or lightheadedness
• with chest discomfort
• with shortness of breath (DYSPNEA)
• in people who have diagnosed forms of CARDIO-
VASCULAR DISEASE (CVD) such as HYPERTENSION,
CORONARY ARTERY DISEASE (CAD), and arrhythmia
disorders
The arrhythmia disorders most likely to include
palpitations among their symptoms are ATRIAL FIB-
RILLATION and PAROXYSMAL ATRIAL TACHYCARDIA (PAT),
also called paroxysmal supraventricular tachycardia
(PSVT). These disorders typically cause periods
of rapid heartbeat. Though disconcerting, these
arrhythmias are rarely dangerous. HYPERTHY-
ROIDISM may also cause palpitations, which go
away with treatment for the hyperthyroidism.
An ELECTROCARDIOGRAM (ECG) provides the necessary
information to determine whether palpitations
indicate an arrhythmia or other heart
problem. A Holter monitor (24-hour recording of
the heart’s electrical activity) and an exercise
STRESS TEST help identify arrhythmias and conduction
disorders that are intermittent or brought on
by physical exertion. Unless there is a significant
underlying arrhythmia disorder, there is no need
to treat palpitations. MEDITATION, relaxation techniques,
and eliminating substances that can have a
stimulant effect on the heart often reduce or end
the palpitations.
See also PREMATURE VENTRICULAR CONTRACTION
(PVC); LONG QT SYNDROME (LQTS); WOLFF-PARKINSON-
WHITE SYNDROME.
paroxysmal atrial tachycardia (PAT) An
ARRHYTHMIA disorder, also called paroxysmal
supraventricular tachycardia (PSVT), in which the
atria have episodes of rapid, regular contractions.
“Paroxysmal” means the symptoms start and stop
abruptly, without apparent cause. During a PAT
episode, the HEART RATE may reach 140 beats per
minute. The atrial contractions of PAT originate in
the atrium above the ATRIOVENTRICULAR (AV) NODE
rather than in the SINOATRIAL (SA) NODE that usually
initiates the heart’s electrical pacing impulses.
The normal path for pacing impulses is from
the SA node through the atria to the AV node.
Many people who have PAT have more than one
conduction pathway at the AV node. Errant electrical
impulses from myocardial cells in the atrium
can activate the alternate pathway, called an
accessory pathway, triggering atrial contractions.
These are called reentrant atrial tachycardias; PAT
is one variation. An episode of PAT may last a few
minutes or several days. The longer the episode
lasts, the more likely it is to produce symptoms.
The primary symptoms of PAT are PALPITATIONS
and lightheadedness, dizziness, or SYNCOPE (fainting).
Some people experience CHEST PAIN, fatigue,
and shortness of breath during an episode of PAT,
though feel fine otherwise. Diagnosis is by ELEC-
TROCARDIOGRAM (ECG), which may require Holter
monitor to capture episodes as they occur. Treatment
may include medications that can disrupt
the accessory AV pathway, such as adenosine or
calcium channel blockers. RADIOFREQUENCY ABLA-
TION, which destroys a small portion of the conductive
pathway to prevent electrical impulses
from traveling it, is often a viable treatment option
for people with recurrent PAT and usually puts a
permanent end to the episodes.
See also ATRIAL FIBRILLATION; HEART; MEDICATIONS
TO TREAT CARDIOVASCULAR DISEASE.