The Heart & Vascualr Center

   In order to understand arrhythmias, one must first have a good understanding of how the heart 
works.  The heart is a hollow muscle - about the size of your fist - located just behind your 
breastbone.  Its job is to pump oxygen rich blood to your body.  The heart consists of four 
chambers divided into the left and right sides by a muscle wall known as the septum. Each side 
consists of an upper chamber called the "atrium" and a lower chamber called the "ventricle". 
Valves between the chambers control the flow of blood within the heart.

   Normally, blood enters the right atrium of the heart and then flows through the tricuspid 
valve into the right ventricle.  From the right ventricle, the blood flows through the pulmonic 
valve and into the lungs.  In the lungs, carbon dioxide is exchanged for oxygen.  From the lungs, 
oxygen-rich blood flows into the left atrium, through the mitral valve, and into the left 
ventricle.  Blood is then pumped through the aortic valve into the aorta (the body's largest 
artery) and is delivered to the rest of the body. 

   The coronary arteries which cover the surface of the heart supply oxygenated blood to the 
heart muscle. The left and right coronary arteries are the main arteries which feed blood from 
the aorta to the heart through a network of branches.  If there is a blockage in any of these 
arteries, this can lead to a change in the heart's ability to pump and in the function of the
heart's electrical system.

   Each normal heartbeat is the result of an electrical impulse.  The heart contains an automatic
electrical system.  In the normal heart, these electrical impulses begin in a tiny area called 
the "Sino-Atrial Node" (the SA node).  This is your heart's own pacemaker which generally keeps 
your heart beating between 60 and 100 times per minute and is related to your level of activity.  
With exercise for example, the SA node increases the rate of impulse information causing your 
heart rate to increase.

   Electrical signals travel along pathways leading to the heart's atria causing them to contract 
or beat. The impulse then moves into the junction between the atria and the ventricles and passes 
through the atrioventricular node (AV node).  The AV node is like a relay station that passes the 
signal down to the ventricles.  It sends its impulses through a pathway called the Bundle of His.  
The rhythmic contractions of the upper and lower chambers of your heart are responsible for the 
smooth flow of blood through the heart. 

   Arrhythmias are abnormalities of heart rhythm. Palpitations are the patient's perception or 
awareness of irregularities in normal heart rhythm.  Symptoms may be "heart pounding," 
"skipping," or a "jumping" sensation in the patient's chest.  More serious symptoms may be 
lightheadedness or loss of consciousness.  These palpitations may be attributed to early 
premature beats from the atrium or ventricle, disturbances of normal heart conduction, abnormal
heart rhythms which may be either too fast or too slow, or disturbances in the function of an 
implanted pacemaker.

   Most patients are not aware of their extra beats, while other patients experience palpitations 
and perceive their extra skipped beats very readily.

   The first step to evaluate a patient with palpitations is a history and physical exam to focus
on the most likely cause for the arrhythmias.  Many arrhythmias, depending upon the clinical
circumstances, can easily be managed as an outpatient. Other more serious arrhythmias require 
in-hospital evaluation and care.

   There are many tests to evaluate cardiac arrhythmias.  Apart from a complete history and
physical, and electrocardiogram (ECG) is often helpful in evaluating patients with cardiac 
arrhythmias and palpitations.  The ECG is able to evaluate patients' conduction abnormalities and 
diagnose previous myocardial infarctions (heart attacks).  It also identifies circumstances which 
may predispose patients to certain arrhythmias. 

   If palpitations are frequently occurring, physicians often order a Holter monitor.  This 
device monitors every heart beat during a 24-hour period. Additionally, patients carry a diary to 
record their specific activities and the exact time of any potential symptoms during the course 
of a day.  A physician can then correlate the patient's symptoms with electrocardiographic 
abnormalities at that time. 

   Frequently, symptoms occur less frequently than every day.  Under these circumstances, 
patients are then given small devices called Event recorders, which is a small hand-held device 
carried by the patient for one month.  When patients have a palpitation, the device records their 
heart rhythm at that exact moment.  This then is another method for physicians to specifically 
evaluate the heart rhythm at a time when the patient is experiencing symptoms. 

   For patients who have an inexplicable loss of consciousness, it may be necessary to be 
admitted to the hospital to evaluate and identify the cause of passing-out.  The hospital 
procedure which evaluates arrhythmias and electrical conduction studies of the heart is called an 
Electrophysiology Study (EPS).  This study is performed in a special laboratory in the hospital 
where the patients under mild sedation have pacemaker catheters inserted through the femoral vein
(groin area) and advanced to the heart.  The heart chambers are then "paced" at different rates 
and an assessment of the patient's "heart wiring" is performed.  This assessment evaluates any 
weakening in the electrical connection of the heart that may require a permanent pacemaker in the 
future.  Additionally, an electrophysiologist will search for the arrhythmias which may be 
correlated to the patient's palpitations and symptoms.  If found, they are studied and their 
source is identified.

   There are several treatments for arrhythmias. Antiarrhythmic drugs are one method which may be
prescribed by your physician.  In some cases, however, antiarrhythmic medications are not  
effective and alternative methods of treatment need to be found. 

   In patients with life-threatening ventricular arrhythmias, in whom medications have not been 
found adequate to prevent their reoccurrence, a cardiac defibrillator may be surgically 
implanted.  These implantable defibrillators are placed in the abdomen, where the generator 
(about the size of a deck of cards) monitors the heart rhythm continuously.  When a dangerous 
ventricular arrhythmia is detected, the internal defibrillator will send an internal shock to
the heart, returning it to a normal rhythm.  The advent of the implantable defibrillator not only 
has been shown to significantly prolong life, but also improve the quality of life.  
Additionally, patients with these defibrillators in most cases no longer require antiarrhythmic 
medications. 

   Other methods of treatment in patients with arrhythmias include sophisticated pacemakers which 
do not perpetually "pace" the heart, but instead monitor the heart's rhythm until a sustained 
arrhythmia occurs.  The pacemaker can then pace the heart at a faster rate which terminates the 
arrhythmia.  Other treatments which are on the horizon include ablation or destruction of heart 
tissue which may be producing an arrhythmia. 

   Like any aspect of heart disease, arrhythmia detection takes some detective work, and there 
are often as many possibilities to consider as there are people with symptoms.  New technology is 
improving the odds for patients who suffer with palpitations, skipped beats, and arrhythmias.  In 
this day and age, it is paramount for physicians to make accurate diagnostic assessments and 
evaluations for patients with arrhythmias so we can offer the best available treatment.