Tachycardia: Difference between revisions

==Ventricular tachycardia==

Ventricular tachycardias (VT's) are rhythm disturbances that arise in the ventricles.  

Symptoms can arise in every ventricular tachycardia, depending on the heart rate, the presence of underlying heart disease and the degree of systolic and diastolic heart failure.  

 

Various symptoms are:  

*Palpitations  

*Abnormal chest sensation  

*Dyspnea  

*Angina  

*Presyncope (lightheadedness, weakness, diaphoresis)  

*Syncope  

*Cardiogenic shock  

Additional information about drug use is mandatory. Toxic levels of digoxin and cocain can lead to VT's. Also additional information about family history of sudden cardiac death is helpfull, as it is a strong predictor of susceptibility to ventricular arrhythmias and sudden cardiac death.  

Although the diagnosis of VT is generally made by a 12 lead ECG, the following physical symptoms may be present:  

*Cannon "A" waves on the jugular venous pulse in the neck. These represent intermittant retrograde propulsion of blood into the jugular veins during right atrial contraction against a closed AV valve. This is evidence of AV dissociation.  

*Decreased or variable amplitude of the carotid or peripheral pulses. This is related to the intermittent periods of atrial and ventricular synchronization, which transiently augment cardiac output.  

*Variable intensity of the first heart sound (although this is difficult with a rapid heart rate).  

*Variable splitting of the first and second heart sounds, and intermittent presence of a third and/or fourth heart sound.  

|+'''An overview of ventricular tachycardias''', follow the Approach to the Wide Complex Tachycardia

!ventricular frequency

!origin (SVT/VT)

| colspan="8" style="text-align:left;background-color:#cfefcf;" | '''Wide complex (QRS>0.12)'''

| ventricle (VT)

| AV-dissociation

| no rate reduction (sometimes accelerates)

| [[Image:vf_small.svg|200px]]

| [[Image:vflutt_small.svg|200px]]

| [[Image:tdp_small.svg|200px]]

! Bundle-branch re-entrant tachycardia*

| [[Image:Bb reentry small.svg|200px]]

|colspan="8"|'''*Bundle-branch re-entrant tachycardia is extremely rare'''

Ventricular tachycardia (VT) is defined as a sequence of three or more ventricular beats. The frequency is often 110-250 bpm. Ventricular tachycardias often origin around old scar tissue in the heart, e.g. after myocardial infarction. Also electrolyte disturbances and ischemia can cause ventricular tachycardias. The cardiac output is often strongly reduced during VT resulting in hypotension and loss of consciousness. VT is a medical emergency as it can deteriorate into ventricular fibrillation and thus mechanical cardiac arrest.

*'''Non-sustained VT:''' three or more ventricular beats with a maximal duration of 30 seconds.  

*Sustained VT: a VT of more than 30 seconds duration (or less if treated by electrocardioversion within 30 seconds).  

*Monomorphic VT: all ventricular beats have the same configuration.  

*Polymorphic VT: the ventricular beats have a changing configuration. The heart rate is 100-333 bpm.  

*Biphasic VT: a ventricular tachycardia with a QRS complex that alternates from beat to beat. Associated with digoxin intoxication and long QT syndrome.  

Determination of the location (or exit site) where a ventricular tachycardia originated, can be helpful in understanding the cause of the VT and is very helpful when planning an ablation procedure to treat a ventricular tachycardia. (new page for localization)  

(Non) sustained VT may be idiopathic, but occurs most frequently in patients with underlying structural heart disease of various types including:  

*Coronary heart disease (CHD) with prior myocardial infarction (is the most frequent cause in developed countries)  

*Hypertrophic cardiomyopathy  

*Dilated cardiomyopathy  

*Mitral valve prolapse  

*Aortic stenosis  

*Complex congenital heart disease  

*Cardiac sarcoidosis  

*Arrhythmogenic RV cardiomyopathy/dysplasia  

'''Hemodynamical instability:''''

*Electrocardioversion  

*Pharmacological treatment can be considered with Procaïnamide or Amiodaron  

Ventricular flutter is a ventricular tachycardia that occurs at a very rapid rate (often around 300 bpm), mostly caused by re-entry. The QRS complexes are regular and usually monomorphic and show a typical sinusoidal pattern. During ventricular flutter the ventricles depolarize in a circular pattern, which prevents good function. Most often this results in a minimal cardiac output and subsequent ischemia. Often deteriorates into ventricular fibrillation.  

Electrocardioversion is the only treatment for ventricular flutter.  

Ventricular fibrillation (VF) is identified by the complete absence of properly formed QRS complexes and no obvious P waves. Instead of uniform activation of the ventricular myocardium, there are uncoördinated series of very rapid, ineffective contractions of the ventricle caused by many chaotic electrical impulses. In recent onset VF the QRS complexes are of high amplitude at rates greater than 320 bpm, which manifest random changes in morphology, width and height. It appears as a completely chaotic rhythm. If VF continues, the fibrillatory waves become fine and can resemble asystole in these cases.  

VF is lethal if the patient is not treated immediately. It gives rise to a mechanical standstill of the heart, because the heart is not able to pump normally anymore. Electrocardioversion is the only treatment for ventricular fibrillation.  

Accelerated idioventricular rhythm (AIVR) is a relatively benign form of ventricular tachycardia. It is (mostly) a regular repetitive ventricular rhythm rate around 60-120 bpm, but mostly 80-100. It is the result of an enhanced ectopic ventricular rhythm, which is faster than normal intrinsic ventricular escape rhythm (<40 bpm), but slower than ventricular tachycardia (over 100-120 bpm). It often occurs during reperfusion after a myocardial infarction. AIVR is not predictive marker for early VF; however, recent debate has started whether among patients with successfull coronary intervention, AIVR is a sign of ventricular dysfunction and therefore a slightly worde prognosis. AIVR can also occur in infants. By this definition, this is a ventricular rhythm of no more than 20% faster than the sinus rate and occuring in the absence of other heart disease. This arrhythmia typically resolves spontaneously during the first months of life (in contrast to an infant with incessant VT which can be due to discrete myocardial tumors or congenital cardiomyopathy).  

AIVR is generally a transient, self-limiting rhythm and resolves as sinus rate surpasses the rate of AIVR. It rarely causes hemodynamic instability and rarely requires treatment.  

Torsades de pointes (TdP) is a ventricular tachycardia associated with a prolonged QTc interval on the resting ECG. It is on the ECG characterized by twisting of the peaks of the QRS complexes around the isoelectric line during the arrhythmia (changing axis). Torsade de pointes is typically initiated by a short-long-short interval. A ventricle extrasystole (first beat: short) is followed by a compensatory pause. The following beat (second beat: long) has a longer QT interval. If the next beat follows shortly thereafter, there is a good chance that this third beat falls within the QT interval, resulting in the R on T phenomenon and subsequent Torsades de pointes.  

*Aquired long QT syndrome (complete list of drugs causing long QT syndrome: [http://www.torsades.org])  

*Congenital long QT syndrome  

Electrocardioversion is the first treatment for TdP.  

To differentiate between supraventricular tachycardias and ventricular tachycardias a 12 lead ECG is the cornerstone of the diagnostic process. At first, the physician has to make a differentiation between a small or broad complex tachycardia.  

====Small complex tachycardia:====

QRS duration < 120 ms.  

A small complex tachycardia is most likely to be a SVT. However, also a septal VT or His-tachycardia can appear as a small complex tachycardia.  

====Broad complex tachycardia:====

QRS duration > 120 ms.  

A broad complex tachycardia can be due to a SVT with aberration, pre-exited tachycardia (eg antidrome re-entry tachycardia) or VT.  

====Treatment====

*Electrical cardioversion  

==References==

#The ESC Textbook of Cardiovascular Medicine. Second edition. Editors: Camm AJ, Luscher TF, Serruys PW. 2009. Oxford university press.

#[http://en.ecgpedia.org ECGpedia:]