Monday, 14 November 2016

P Wave Asystole

Another form of Asystole you may encounter is called P wave asystole or Ventricular Asystole. The features are the same as traditional Asystole, but with one exception, there will be P waves present in the ECG tracing. The patient is clinically dead. The patient will not survive with just atrial depolarization and will require CPR.


Asystole, also known as flatline, is a state of no electrical activity from the heart and therefore no blood flow. It results in cardiac arrest. Survival rates in a cardiac arrest patient with asystole are much lower than a patient with a rhythm amenable to defibrillation; asystole is itself not a "shockable" rhythm.

Ventricular Standstill

Ventricular standstill is the absence of any ventricular activity for more than a few seconds. There may be atrial activity as evidenced by P waves in which case complete heart block is blocking all impulses from reaching the ventricles and the backup or subsidiary pacemaker has failed, or there may be an absence of atrial and ventricular activity.

Agonal Rhythm

An agonal heart rhythm is a variant of asystole with a heart rate is less than 20 bpm, without P waves and with wide, bizarre QRS complexes seen on the electrocardiogram. Clinically, an agonal rhythm is regarded as asystole and should be treated equivalently, with cardiopulmonary resuscitation. As in asystole, the prognosis for a patient presenting with this rhythm is very poor.

3rd Degree AV Block

Third-degree atrioventricular block (AV block), also known as complete heart block, is a medical condition in which the impulse generated in the sinoatrial node (SA node) in the atrium of the heart does not propagate to the ventricles.

Because the impulse is blocked, an accessory pacemaker in the lower chambers will typically activate the ventricles. This is known as an escape rhythm. Since this accessory pacemaker also activates independently of the impulse generated at the SA node, two independent rhythms can be noted on the electrocardiogram (ECG).
  • The P waves with a regular P-to-P interval (in other words, a sinus rhythm) represent the first rhythm.
  • The QRS complexes with a regular R-to-R interval represent the second rhythm. The PR interval will be variable, as the hallmark of complete heart block is lack of any apparent relationship between P waves and QRS complexes.
Patients with third-degree AV block typically experience severe bradycardia (an abnormally low measured heart rate), hypotension, and at times, hemodynamic instability.

Second Degree AV Block Mobitz Type 2

Type 2 Second-degree AV block, also known as "Mobitz II," is almost always a disease of the distal conduction system (His-Purkinje System).

Mobitz II heart block is characterized on a surface ECG by intermittently nonconducted P waves not preceded by PR prolongation and not followed by PR shortening. There is usually a fixed number of non-conducted P waves for every successfully conducted QRS complex, and this ratio is often specified in describing Mobitz II blocks. For example, Mobitz II block in which there are two P waves for every one QRS complex may be referred to as "2:1 Mobitz II block".

The medical significance of this type of AV block is that it may progress rapidly to complete heart block, in which no escape rhythm may emerge. In this case, the person may experience a Stokes-Adams attack, cardiac arrest, or sudden cardiac death. The definitive treatment for this form of AV Block is an implanted pacemaker.

The impairment is usually below the AV node. Although the terms infranodal block or infrahisian block are often applied to this disorder, they refer to the anatomic location of the block, whereas Mobitz II refers to an electrocardiographic pattern.

Second Degree AV Block Mobitz Type I (wenckebach)

Type 1 Second-degree AV block, also known as Mobitz I or Wenckebach periodicity, is almost always a disease of the AV node.

Mobitz I heart block is characterized by progressive prolongation of the PR interval on the electrocardiogram (ECG) on consecutive beats followed by a blocked P wave (i.e., a 'dropped' QRS complex). After the dropped QRS complex, the PR interval resets and the cycle repeats.

One of the baseline assumptions when determining if an individual has Mobitz I heart block is that the atrial rhythm has to be regular. If the atrial rhythm is not regular, there could be alternative explanations as to why certain P waves do not conduct to the ventricles.
This is almost always a benign condition for which no specific treatment is needed. In symptomatic cases, intravenous atropine may transiently improve conduction.

First Degree AV Bock

First-degree atrioventricular block (AV block), or PR prolongation, is a disease of the electrical conduction system of the heart in which the PR interval is lengthened beyond 0.20 seconds.

In first-degree AV block, the impulse conducting from atria to ventricles through the atrioventricular node (AV node) is delayed and travels slower than normal.

Ventricular Hexageminy

Hexageminy — every sixth beat is a PVC.

Ventricular Pentageminy

Pentageminy — every fifth beat is a PVC.

Ventricular Quadrigeminy

Quadrigeminy — every fourth beat is a PVC.

Ventricular Trigeminy

The ECG trace above shows ventricular trigeminy; the ventricular ectopic beats (2nd, 5th, 8th, and 11th) are separated by two sinus beats.

Ventricular Bigeminy

Bigeminy or bigemini is a heart rhythm problem in which there is a continuous alternation of long and short heart beats. Most often this is due to ectopic beats occurring so frequently that there is one after each sinus beat. The two beats are figuratively two twins (hence bi- + gemini). The ectopic beat is typically a premature ventricular contraction (PVC). For example, in ventricular bigeminy, a sinus beat is shortly followed by a PVC, a pause, another normal beat, and then another PVC. In atrial bigeminy, the other "twin" is a premature atrial contraction (PAC).

After any PVC there is a pause that can lead to the development of bigeminy. A PVC wavefront often encounters a refractory AV node that does not conduct the wavefront retrograde. Thus the atrium is not depolarized and the sinus node is not reset. Since the sinus p wave to PVC interval is less than the normal P-P interval, the interval between the PVC and the next p wave is prolonged to equal the normal time elapsed during two P-P intervals. This is called a "compensatory" pause. The pause after the PVC leads to a longer recovery time which is associated with a higher likelihood of myocardium being in different stages of re-polarization. This then allows for re-entrant circuits and sets up the ventricle for another PVC after the next sinus beat. The constant interval between the sinus beat and PVC suggests a reentrant etiology rather than spontaneous automaticity of the ventricle.

Atrial premature complexes (APCs) do not have a compensatory pause since they reset the sinus node but atrial or supraventricular bigeminy can occur. If the APCs are very premature, the wave front can encounter a refractory AV node and not be conducted. This can be mistaken for sinus bradycardia if the APC is buried in the t wave since the APC will reset the SA node and lead to a long P-P interval.

Ventricular Triplets (salvo)

The appearance of 3 consecutive PVCs is called as ventricular triplet, ventricular salvo or non-sustained ventricular tachycardia, (if the duration is self terminating within 30 seconds).  

Ventricular Couplets

The above is an example of a ventricular couplet or two consecutive PVCs.

Multifocal PVCs

Multifocal PVCs all look different from each other on the same ECG. They occur at different intervals, at various times in the QRS cycle, with different coupling intervals. Multiformed PVCs usually have the same coupling intervals (because they originate in the same ectopic site but their conduction through the ventricles differ. Multiformed PVCs are common in digitalis intoxication.

Premature Ventricular Contraction (PVC)

A premature ventricular contraction (PVC) — also known as a premature ventricular complex, ventricular premature contraction (or complex or complexes) (VPC), ventricular premature beat (VPB), or ventricular extrasystole (VES) — is a relatively common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node, the normal heartbeat initiator. The electrical events of the heart detected by the electrocardiogram (ECG) allow a PVC to be easily distinguished from a normal heart beat. Although a PVC can be a sign of decreased oxygenation to the heart muscle, often PVCs are benign and may even be found in otherwise healthy hearts.

A PVC may be perceived as a "skipped beat" or felt as palpitations in the chest. In a normal heartbeat, the ventricles contract after the atria have helped to fill them by contracting; in this way the ventricles can pump a maximized amount of blood both to the lungs and to the rest of the body. In a PVC, the ventricles contract first and before the atria have optimally filled the ventricles with blood, which means that circulation is inefficient. However, single beat PVC abnormal heart rhythms do not usually pose a danger and can be asymptomatic in healthy individuals. A PVC is a type of ectopic beat.

Ventricular Fibrillation (VF)

Ventricular fibrillation (V-fib or VF) is when the heart quivers instead of pumps due to disorganized electrical activity in the ventricles. It results in cardiac arrest with loss of consciousness and no pulse. This is followed by irreversible death in the absence of treatment. Ventricular fibrillation is found initially in about 10% of people in cardiac arrest.

Ventricular fibrillation can occur due to coronary heart disease, valvular heart disease, cardiomyopathy, Brugada syndrome, long QT syndrome, or intracranial haemorrhage. Diagnosis is by an electrocardiogram (ECG) showing irregular unformed QRS complexes without any clear P waves. An important differential diagnosis is torsade's de pointes.

Treatment is with cardiopulmonary resuscitation (CPR) and defibrillation. Biphasic defibrillation may be better than monophasic.

Ventricular Tachycardia (VT)

Ventricular tachycardia (V-tach or VT) is a type of regular and fast heart rate that arises from improper electrical activity in the ventricles of the heart. Although a few seconds may not result in problems, longer periods are dangerous. Short periods may occur without symptoms or present with lightheadedness, palpitations, or chest pain. Ventricular tachycardia may result in cardiac arrest and turn into ventricular fibrillation. Ventricular tachycardia is found initially in about 7% of people in cardiac arrest.

Ventricular tachycardia can occur due to coronary heart disease, aortic stenosis, cardiomyopathy, electrolyte problems, or a heart attack. Diagnosis is by an electrocardiogram (ECG) showing a rate of greater than 120 bpm and at least three wide QRS complexes in a row. It is classified as non-sustained versus sustained based on whether or not it lasts less than or more than 30 seconds. The term "ventricular tachycardias" refers to the group of irregular heartbeats that includes ventricular tachycardia, ventricular fibrillation, and torsades de pointes.

Ventricular Flutter

Ventricular flutter is an arrhythmia, more specifically a tachycardia affecting the ventricles with a rate over 250-350 beats/min. It is characterized on the ECG by a sinusoidal waveform without clear definition of the QRS and T waves. It has been considered as a possible transition stage between ventricular tachycardia and fibrillation, and is a critically unstable arrhythmia that can result in sudden cardiac death. It can occur in infancy, youth, or as an adult. It can be induced by programmed electrical stimulation.

Polymorphic Ventricular Tachycardia (PVT)

Polymorphic ventricular tachycardia (PVT) is a form of ventricular tachycardia in which there are multiple ventricular foci with the resultant QRS complexes varying in amplitude, axis and duration. The commonest cause of PVT is myocardial ischaemia.

Accelerated Idioventricular Rhythm (AIVR)

Accelerated idioventricular rhythm is ventricular rhythm with a rate of between 40 and 120 beats per minute. Idioventricular means “relating to or affecting the cardiac ventricle alone“ and refers to any ectopic ventricular arrythmia. Accelerated idioventricular arrhythmias are distinguished from ventricular rhythms with rates less than 40 (ventricular escape) and those faster than 120 (ventricular tachycardia). Though some other references limit to between 60 and 100 beats per minute. It is also referred to as AIVR and "slow ventricular tachycardia."

It can be present at birth. However, it is more commonly associated with reperfusion after myocardial injury.

Idioventricular Rhythm

Normally, the pacemaker of the heart that is responsible for triggering each heart beat (ventricular contraction) is the SA (Sino Atrial) node. However, if the ventricle does not receive triggering signals at a rate high enough from either the SA node or the AV (Atrioventricular) node, the ventricular myocardium itself becomes the pacemaker (escape rhythm). This is called Idioventricular Rhythm. Ventricular signals are transmitted cell-to-cell between cardiomyocytes and not by the conduction system, creating wide sometimes bizarre QRS complexes (> 0.12 sec). The rate is usually 20-40 bpm.

If the rate is >40 bpm, it is called accelerated idioventricular rhythm. The rate of 20-40 is the "intrinsic automaticity" of the ventricular myocardium. It can be regarded as a "backup plan" or "redundancy" built into the body.

Premature Junctional Complex (PJC)

The 5th beat on the rhythm strip above shows a PJC complex

Premature junctional contractions (PJCs), also called atrioventricular junctional premature complexes or junctional extrasystole, are premature cardiac electrical impulses originating from the atrioventricular node of the heart or "junction." This area is not the normal but only a secondary source of cardiac electrical impulse formation. These premature beats can be found occasionally in healthy people and more commonly in some pathologic conditions, typically in the case of drug cardiotoxicity, electrolyte imbalance, mitral valve surgery, and cold water immersion. If more than two such beats are seen, then the condition is termed junctional rhythm. On the surface ECG, premature junctional contractions will appear as a normally shaped ventricular complex or QRS complex, not preceded by any atrial complex or P wave or preceded by an abnormal P wave with a shorter distance or interval between the P wave and the QRS. Rarely, the abnormal P wave can follow the QRS.

Junctional Tachycardia

Junctional tachycardia is a form of supraventricular tachycardia characterized by involvement of the AV node. It can be contrasted to atrial tachycardia. It is a tachycardia associated with the generation of impulses in a focus in the region of the atrioventricular node due to an AV disassociation. In general, the AV junction's intrinsic rate is 40-60 bpm so junctional tachycardia implies a rate >60 bpm.

On an ECG, Junctional Tachycardia exhibits the following classic criteria:
  • P Waves: The P Wave may be inverted in leads II, III and aVF or not visible
  • Narrow QRS complexes (which is consistent with non-ventricular rhythms)
It can coexist with other superventricular tachycardias due to the disassociation between the SA node and the AV node. Junctional Tachycardia can appear similar to atrioventricular nodal reentrant tachycardia (AVNRT). One form is junctional ectopic tachycardia.

Accelerated Junctional Rhythm

Accelerated junctional rhythm occurs when the AV junction fires impulses at above 60 bpm. Rhythm will be very regular. The QRS complex is narrow (0.10 sec or less).

Junctional Escape Rhythm/Complex

A junctional escape beat is a delayed heartbeat originating not from the atrium but from an ectopic focus somewhere in the AV junction. It occurs when the rate of depolarization of the sinoatrial node falls below the rate of the atrioventricular node. This dysrhythmia also may occur when the electrical impulses from the SA node fail to reach the AV node because of SA or AV block. It is a protective mechanism for the heart, to compensate for the SA node no longer handling the pacemaker activity, and is one of a series of backup sites that can take over pacemaker function when the SA node fails to do so.

A junctional escape complex is a normal response that may result from excessive vagal tone on the SA node (e.g. digoxin toxicity), a pathological slowing of the SA discharge, or a complete AV block. Junctional rhythms (if a bradycardia) can cause decreased cardiac output. Therefore, the person may exhibit signs and symptoms similar to other bradycardia such as lightheadedness, dizziness, hypotension, and syncope. This rhythm can usually be tolerated if the rate is above 50 bpm.

ECG Characteristics:

  • Rate: 40-60 bpm
  • Rhythm: Irregular in single junctional escape complex; regular in junctional escape rhythm.
  • P waves: Depends on the site of the ectopic focus. They will be inverted, and may appear before or after the QRS complex, or they may be absent, hidden by the QRS.
  • PR interval: If the P wave occurs before the QRS complex, the interval will be less than 0.12 seconds.
  • QRS Complex: Usually normal in duration and morphology, less than 0.12 seconds.