Tachycardia: Difference between revisions
→Ventricular tachycardia
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===History=== | ===History=== | ||
Symptoms can arise in every ventricular tachycardia, depending on the heart rate, the presence of underlying heart disease and the degree of systolic heart failure. Various symptoms are: | 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 | * Palpitations | ||
* Abnormal chest sensation | * Abnormal chest sensation | ||
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===Diagnostic Evaluation=== | ===Diagnostic Evaluation=== | ||
*'''Exercise testing:''' Exercise testing is recommended in adult patients with ventricular tachycardias who have an intermediate or greater probability of having coronary heart disease by age, gender and symptoms. It is meant to provoke ischemic changes or ventricular arrhythmias. | |||
''' | *'''Ambulatory (Holter) ECG:''' Ambulatory ECG is necessary if the diagnosis needs to be clarified, by detecting arrhythmias, QT-interval changes, T-wave alternans (TWA) or ST-segment changes. | ||
''' | *'''Echocardiography, Cardiac CT, MRI:''' Echocardiography is recommended in patients with ventricular tachycardias who are suspected of having a structural heart disease. If echocardiography does not provide accurate assessment of the left and right ventricular function and/or structural changes, cardiac CT or MRI can be done. | ||
''' | *'''Exercise testing with an image modality (echocardiography or nuclear perfusion):''' Some patients with ventricular arrhythmias have an intermediate probability of coronairy heart disease, but their ECG is less reliabe (because of digoxin use, LVH, greater than 1mm ST-segment depression at rest, WPW syndrome or LBBB). For detecting silent ischemia in these patients exercise testing with an image modality can be done. If patients are unable to perform exercise, a pharmacological stress test with an imaging modality can be done. | ||
''' | *'''Coronary angiography:''' Coronary angiography can diagnose or exclude the presence of significant obstructive coronairy heart disease in patients with ventricular arrhythmias who have an intermediate or greater probability of having coronairy heart disease. | ||
''' | *'''Electrophysiological testing:''' Electrophysiological testing can be performed to guide and assess the efficacy of VT ablation in patients with ventricular arrhythmias. It can also be done to clarify the mechanism of broad complex tachycardias in patients with coronairy heart disease. | ||
===Overview of ventricular tachycardias=== | |||
: | (figure: overview of ventricular tachycardias) | ||
==Ventricular tachycardia== | ==Ventricular tachycardia== | ||
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 conciousness. VT is a medical emergency as it can deteriorate into ventricular fibrillation and thus mechanical cardiac arrest. | 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 conciousness. VT is a medical emergency as it can deteriorate into ventricular fibrillation and thus mechanical cardiac arrest. | ||
===Definitions | ===Definitions=== | ||
*'''Non-sustained VT''': three or more ventricular beats with a maximal duration of 30 seconds. | *'''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). | *'''Sustained VT''': a VT of more than 30 seconds duration (or less if treated by electrocardioversion within 30 seconds). | ||
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*'''Biphasic VT''': a ventricular tachycardia with a QRS complex that alternates from beat to beat. Associated with digoxin intoxication and long QT syndrome. | *'''Biphasic VT''': a ventricular tachycardia with a QRS complex that alternates from beat to beat. Associated with digoxin intoxication and long QT syndrome. | ||
===Localisation of the origin of a ventricular tachycardia | ===Localisation of the origin of a ventricular tachycardia=== | ||
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) | 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) | ||
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==Ventricular flutter== | ==Ventricular flutter== | ||
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. | |||
===Treatment=== | |||
Electrocardioversion is the only treatment for ventricular flutter. | |||
==Ventricular fibrillation== | ==Ventricular fibrillation== | ||
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. | 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. | ||
==Torsade de | |||
===Treatment=== | |||
Electrocardioversion is the only treatment for ventricular fibrillation. | |||
==Accelerated idio-ventricular rhythm== | |||
==Torsades de Pointes== | |||
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. | |||
===Differential diagnosis=== | |||
* Aquired long QT syndrome (drugs causing long QT syndrome: http://www.azcert.org/medical-pros/drug-lists/drug-lists.cfm) | |||
* Congenital long QT syndrome | |||
===Treatment=== | |||
Electrocardioversion is the first treatment for TdP. | |||
Additional treatments are: | |||
* Withdrawal of any offending drugs and correction of electrolyte abnormalities (potassium repletion up to 4.5 to 5 mmol/liter). | |||
* Acute and long-term cardiac pacing in patients with TdP presenting with heart block, symptomatic bradycardia or recurrent pause-dependent TdP | |||
* Intravenous magnesium sulfate for patients with QT prolongation and few episodes of TdP. | |||
* Beta blockers combined with cardiac pacing as acute therapy for patients with TdP and sinus bradycardia. | |||
* Isoproterenol as temporary treatment in patients with recurrent pause-dependent TdP who do not have congenital long QT syndrome. | |||
=Differentiation between SVT and VT= | =Differentiation between SVT and VT= | ||