Electrophysiology

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sinoatrial node (SA node)

Back 1

The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node (SA node) of the heart to be propagated to (and stimulate) the myocardium (muscle of the heart)

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Atrial flutter

Back 2

Atrial flutter is a rhythmic, fast rhythm that occurs in the atria of the heart. This rhythm occurs most often in individuals with organic heart disease (ie: pericarditis, coronary artery disease, and cardiomyopathy).
Atrial flutter is typically not a stable rhythm, and frequently degenerates to atrial fibrillation. In the case of atrial flutter, there is a very particular block pattern at the AV node level. In atrial flutter, the AV node typically will block every other electrical impulse, or three out of four impulses. If every other impulse is blocked, known as 2:1 block, while the atrial rate is 300 beats/minute, the ventricular rate will be 150 beats/minute. If three out of four beats are blocked, known as 4:1 block, while the atrial rate is 300 beats/minute, the ventricular rate will be 75 beats/minute.

Front 3

atrioventricular node (abbreviated AV node)

Back 3

the tissue between the atria and the ventricles of the heart, which conducts the normal electrical impulse from the atria to the ventricles. An important property that is unique to the AV node is decremental conduction. This is the property of the AV node that prevents rapid conduction to the ventricle in cases of rapid atrial rhythms, such as atrial fibrillation or atrial flutter

Front 4

Atrial fibrillation (AF or afib

Back 4

is an abnormal heart rhythm (cardiac arrhythmia) which involves the two small, upper heart chambers (the atria). Heart beats in a normal heart begin after electricity generated in the atria by the sinoatrial node spread through the heart and cause contraction of the heart muscle and pumping of blood. In AF, the regular electrical impulses of the sinoatrial node are replaced by disorganized, rapid electrical impulses which result in irregular heart beats.

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Recurrent

Back 5

Any patient with 2 or more identified episodes of atrial fibrillation is said to have recurrent atrial fibrillation. This is further classified into paroxysmal and persistent based on when the episode terminates without therapy.

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Paroxysmal

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Atrial fibrillation is said to be paroxysmal when it terminates spontaneously within 7 days, most commonly within 24 hours.

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Persistent

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Persistent or chronic atrial fibrillation is AF established for more than seven days. Differentiation of paroxysmal from chronic or established AF is based on the history of recurrent episodes and the duration of the current episode of AF

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Lone atrial fibrillation

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Lone atrial fibrillation (LAF) is defined as atrial fibrillation in the absence of clinical or echocardiographic findings of cardiopulmonary disease. [4] Patients with LAF who are under 65 have the best prognosis.

Front 9

Electrocardiogram

Back 9

Atrial fibrillation is diagnosed on an electrocardiogram, an investigation performed routinely whenever irregular heart beat is suspected. Characteristic findings are (a "rhythm strip" of lead II is shown):

absence of P waves
unorganized electrical activity in their place
irregularity of R-R interval due to irregular conduction of impulses to the ventricles

Front 10

atrial fibrillation vs. atrial flutter

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In atrial fibrillation, the regular impulses produced by the sinus node to provide rhythmic contraction of the heart are overwhelmed by the rapid randomly generated discharges produced by larger areas of atrial tissue. It can be distinguished from atrial flutter, which is a more organized electrical circuit usually in the right atrium that produces characteristic saw toothed waves on the electrocardiogram.

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main goals of treatment of atrial fibrillation

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The main goals of treatment of atrial fibrillation are to prevent temporary circulatory instability and to prevent stroke. Rate and rhythm control are principally used to achieve the former, while anticoagulation may be required to decrease the risk of the latter

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AFib symptoms

Back 12

Palpitations, angina(chest pain), lassitude (weariness), and decreased exercise tolerance are related to rapid heart rate and inefficient cardiac output caused by AF

Front 13

Tachycardia

Back 13

Tachycardia is an abnormally rapid beating of the heart, defined as a resting heart rate of over 100 beats per minute.

It can have harmful effects in two ways. First, when the heart beats too rapidly, it performs inefficiently (since there is not enough time for the ventricles to fill completely), causing blood flow and blood pressure to diminish. Second, it increases the work of the heart, causing it to require more oxygen while also reducing the blood flow to the cardiac muscle tissue, increasing the risk of ischemia(restricted blood supply) and resultantly infarction(dead tissue)

Front 14

Supraventricular tachycardia (SVT)

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SVT) occurs when an abnormal electrical impulse originates above the ventricles, but instead of causing a single beat and a pause, it travels in circles and causes many rapid beats. To distinguish SVT from Sinus Tachycardia one must simply look at the rate: If the rate of contraction is more than 150 bpm, then it is considered SVT. Otherwise it is Sinus Tachycardia.

Front 15

Ventricular tachycardia (VT or "V-tach")

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Ventricular tachycardia (VT or "V-tach") is a similar phenomenon occurring within the tissue of the ventricles, causing an extremely rapid rate with poor pumping action. Both of these rhythms normally last for only a few seconds (paroxysmal tachycardia), but if VT persists it is extremely dangerous, often leading to ventricular fibrillation.

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Ventricular fibrillation (V-fib or VF)

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Ventricular fibrillation (V-fib or VF) is a cardiac condition that consists of a lack of coordination of the contraction of the muscle tissue of the large chambers of the heart that eventually leads to the heart stopping altogether. Ventricular fibrillation is considered a medical emergency. If the arrhythmia continues for more than a few seconds, blood circulation will cease, as evidenced by lack of pulse, blood pressure and respiration, and death will occur.
Ventricular fibrillation is a cause of cardiac arrest and sudden cardiac death.

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Vagus reflex

Back 17

The vagus nerve plays a role in (amongst other things) controlling the pulse. The vagus reflex is a reaction which can reduce the pulse rate during tachycardia (racing pulse). The following stimuli may produce the vagus reflex:
- tensing the lower abdomen (precaution needed while in bathroom.)
- gentle pressure on the closed eyes
- a gulp of ice-cold water
- splashing ice-cold water on the face
- immersing the arms in ice-cold water
- finger stuck down the throat
- the insertion of an IV needle

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Radiofrequency ablation (RFA)

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uses radiofrequency(RF) energy to destroy(ablate) abnormal electrical pathways in heart tissue. It is used in recurrent AF. The energy emitting probe (electrode) is placed into the heart through a catheter. The practitioner first "maps" an area of the heart to locate the abnormal electrical activity before the responsible tissue is eliminated. Ablation is a newer technique and has shown some promise for cases unresponsive to conventional treatments

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Other ablation techniques

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New techniques include the use of cryoablation (tissue freezing using a coolant which flows through the catheter), and microwave ablation, where tissue is ablated by the microwave energy "cooking" the adjacent tissue. The abnormal electrophysiology can also be modified in a similar way surgically, and this procedure referred to as the Cox maze procedure

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Anticoagulation

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In confirmed AF, anticoagulant treatment is a crucial way to prevent stroke. Treatment of AF patients over age 60 with warfarin (also known as Coumadin® or Marevan®) results in a significant reduction in the subsequent risk of stroke. Patients under age 65 who have any structural heart disease (i.e. valvular heart disease, ejection fraction <= 35%, history of heart attack) also benefit from warfarin.

The use of warfarin is associated with a delayed clinical effect. It typically takes three to five days to achieve a demonstrable anticoagulant effect, and in this time, physicians commonly use heparin or other heparinoids such as enoxaparin to provide early anticoagulation.

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postural orthostatic tachycardia syndrome (POTS)

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a sudden drop of blood pressure that occurs with a change in body position (e.g., going from lying down to standing up)

Front 22

sinus tachycardia

Back 22

If the heart's electrical system is functioning normally, except that the rate is in excess of 100 beats per minute

Front 23

Supraventricular tachycardia (SVT)

Back 23

occurs when an abnormal electrical impulse originates above the ventricles, but instead of causing a single beat and a pause, it travels in circles and causes many rapid beats. To distinguish SVT from Sinus Tachycardia one must simply look at the rate: If the rate of contraction is more than 150 bpm, then it is considered SVT. Otherwise it is Sinus Tachycardia.

Front 24

Ablation (radiofrequency)

Back 24

Deactivation or removal by interruption of cells through controlled heating of tissues.

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Angioplasty

Back 25

Surgical repair of a blood vessel. During balloon angioplasty, an obstructed blood vessel is repaired by dilating it with a balloon catheter. As shown in this picture, the balloon and stent on the catheter presses against the vessel wall, resulting in the compression of the plaque that is causing the obstruction.
See alsoPTCA.

Front 26

Atrium

Back 26

An internal chamber or "entrance hall", at the upper portion on either side of the heart. The atria transmit blood to the corresponding ventricles of the heart (right to right; left to left). Plural is Atria

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Bradycardia

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Abnormally slow rhythm.

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Catheter

Back 28

A tubular instrument made of a flexible material, inserted into the body for diagnostic/treatment purposes.

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Cardiac Catheterization

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Passage of a long, fine catheter through a blood vessel into the chambers of the heart, as an aid in diagnosis and/or treatment of various heart disorders and anomalies.

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Electrocardiogram (ECG, EKG)

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A tracing representing the heart's electrical action, derived by amplification of the minutely small electrical impulses normally generated by the heart.

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Infarction

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The development or presence of a localized area (of the heart) with deficient or impeded blood supply and/or resultant dead muscle tissue.

The word infarction is from the Latin, meaning an area of dead tissue resulting from obstruction of the local circulation

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Myocardial Infarction

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The medical term for a heart attack.

The word myocardial is from the Latin and Greek, meaning the middle muscular layer of the heart.

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Myocardium

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The muscular substance of the heart.

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Stents

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A stent is a wire mesh tube used to hold open a vessel that has been cleared of excess plaque. Once placed inside the vessel via an angioplasty balloon catheter, the stent helps to keep the vessel open (see picture), resulting in improved blood flow to the heart muscle.

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SVT

Back 35

Supraventricular tachycardia, i.e., an abnormally fast heart rhythm that originates above the ventricles.

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Tachycardia

Back 36

Abnormally fast rhythm.

Front 37

Transmyocardial Revascularization

Back 37

An open heart procedure during which the physician uses a laser to cut a series of channels in the sick heart muscle to increase blood flow to it.
A newer technique is Percutaneous Transmyocardial Revascularization, which enables the same technique from inside the heart, during a catheterization procedure.

Front 38

Ventricle

Back 38

A small cavity or chamber in the heart. The heart has two ventricles, one on the left and one on the right.