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Ventricular tachycardia

Ventricular Tachycardia (VT) is a tachycardia arising fromone of the ventricles. It may arise from either the right or the left ventricle. It can be caused either by a diseased focus in the myocardium itself or by a large reentry circuit involving the bundle branches and/or the bundle of His.

Symptoms of VT

Patients usually have “spells” consisting symptoms of abnormal heart beating (“palpitations”) or out right heart racing. Associated symptoms may include chest pain, pulsations in the neck, shortness of breath, light-headedness, fatigue, sweating, etc. Patients may pass out with VT or even have a cardiac arrest.

Diagnosis of VT

VT can be documented by a 12 lead ECG performed at the time that the patient’s heart is racing if the patient goes to the emergency room. Patients who have daily episodes of VT can have a 24-hour holter monitor placed to document the VT. More commonly, patients may have monthly episodes and can use an external event monitor to record episodes and call them in to a toll-free telephone number. More rare episodes are difficult to document unless the patient waits until an episode occurs and then seeks medical attention at an emergency room or physician’s office. Patients who call 911 may have their episode of VT documented by the paramedics en route to the hospital. Patients who are in the hospital wearing a telemetry monitor will have their VT documented. Internal looped monitors are not usually deployed just to document VT. However when such monitors are inserted in patients with syncope, VT is occasionally documented. The heart rate of VT is from 130 to nearly 300 beats per minute. Usually, the heart rate is between 160 and 220 beats per minute. Sometimes it takes an electrophysiology study or EPS to diagnose VT.

Advice to patients with VT

People frequently ask what to do when they have an episode of heart racing. The most important factor is to use common sense. If the person feels very bad as they usually do with VT (severe chest pain, severe shortness of breath) or passes out then calling 911 is prudent. If the person collapses, is apneic, and has no pulse, call 911 and start CPR. Vagal maneuvers seldom work for VT. Patients must go promptly to the emergency room.

Emergency care for VT

A physician, after recording an ECG or rhythm strip and assessing the patient’s vital signs will decide whether the person is unstable or not. If an emergency exists, the patient will be sedated and external cardioversion performed. If the patient is stable, the physician will order a 12 lead ECG, which records the VT. If the physician is not sure whether the tachycardia is VT, they may ask the patient to perform vagal maneuvers to see if sinus rhythm can be restored. Since this usually does is ineffective, IV medications are then given. Adenosine, a medications good for converting SVT is sometimes administered if the physician is unsure of the diagnosis. It is better to avoid this, but given the brief half-life of adenosine, it usually does not produce hemodynamic collapse. Definitive medications such as lidocaine, procainamide or amiodarone are given adhering to published ACLS guidelines. If nothing succeeds in restoring sinus rhythm, then eventually external cardioversion is performed. Usually once sinus rhythm is restored, the person with VT is admitted to the hospital for further workup.

Prognosis and workup of VT

Persons with VT should be seen initially by a cardiologist. The typical workup of patients with VT involves having an echocardiogram done to assess for structural heart disease. Patients with prominent symptoms of or risk factors for coronary artery disease may need stress testing or even a coronary angiogram. Usually, patients with VT have had heart attacks or have a cardiomyopathy from hypertension, valvular heart disease, or a viral infection affecting the myocardium. Some patients may need open heart surgery. In patients with structural heart disease, VT is a life-threatening emergency, and nearly all patients have implantable cardiac defibrillator devices (ICD) deployed since studies comparing ICD with antiarrhythmic drug therapy have clearly shown ICD therapy to be superior. Only if frequent episodes of VT recur and are not responsive to antiarrhythmics does ablation become an option. Occasionally there is a patient with a small previous infarction who has only 1 site of VT: ablation without an ICD would be an option in this case. Rare patients may present with incessant VT. In these patients, ICD therapy is contraindicated and antiarrhythmic drugs therapy or ablation is more appropriate as an initial strategy.

In more rare patients there is no structural heart disease at all - this type of VT is called idiopathic. The prognosis of these patients is excellent. Idiopathic VT does not lead to cardiac arrest, stroke or myocardial infarction. However, VT will recur at some point in nearly all patients at some point. For patients who have just experienced their first episode of idiopathic VT, it is impossible to say when the next episode will occur – it could be one week, one month or one to several years. For this reason, many such patients take a wait and see approach to their idiopathic VT. As years pass, nearly every patient experiences more frequent and/or more long-lasting episodes.

Treatment options for VT

Patients with VT who have structural heart disease virtually always need an ICD implanted since ICD therapy prolongs life by preventing the VT from causing a cardiac arrest. These patients will not usually need ablation and will not be discussed further since the focus of this website is curative ablation. However, animal studies suggest that cryoablation might make large enough freezes in areas of the border of an infarct to possibly cure VT arising after myocardial infarction (1).

Patients with idiopathic VT are not at risk for cardiac arrest, heart attack, death or stroke. Because of this, the treatment of idiopathic VT does not prolong life. The only other reason to treat idiopathic VT therefore is to alleviate the symptoms. There are rare patients who are in incessant idiopathic VT (at least 90% of the day with average heart rates over 130 beats per minute). Such patients may develop a tachycardiomyopathy in which case treatment is mandatory.

Patients with idiopathic VT have four general options for therapy:

  1. Doing nothing but just living with it
  2. Taking medications to prevent it
  3. Having ablation for cure, or
  4. Having open-heart surgery

Living with idiopathic VT (no therapy)

This is a good option for patients with rare episodes that are associated with lower heart rates (usually less than 150 beats per minute) and only minor symptoms. Such patients when they experience VT can try vagal maneuvers at home or even try to fall asleep in hopes that the VT will go away on its own. After some period of time, such patients eventually must go to the emergency room if their VT does not go away. Usually intravenous drugs are required to stop VT. Frequent visits to the emergency room are inconvenient and expensive, such that many patients eventually decide on some form of therapy.

Treatment of idiopathic VT with antiarrhythmics

Antiarrhythmic drugs can be given occasionally when a VT episode occurs – this so-called “pill in the pocket” approach involves the patient taking a large single dose of an antiarrhythmic medication and then waiting for a few hours to see if VT goes away. Flecainide or propafenone are the most common medications used. This approach is only safe for patients who tolerate their VT well with minimal symptoms.

Daily heart-rhythm medication is a better option if VT is more frequent and/or not as well tolerated by the patient. The physician starts a medication and asks the patient to notify them if any side effects occur. If none occur, the dose of the medication is increased until there is a good chance that it might work for the patient. If VT never recurs, the patient takes the medication the rest of their life. If VT recurs, the physician has the option of increasing the dose or trying another medication. The milder medications (beta blockers, calcium channel blockers) are the safest and the least expensive. They have moderate efficacy and moderate side effects. However some patients need to be on such medications for other reasons such as hypertension or migraine headaches. In these patients, such medications should generally be tried before considering other medications or ablation.

There are stronger antiarrhythmic drugs for patients who fail the milder medications. These medications consist of flecainide, propafenone, and sotalol. These three medications are less likely to cause side effects and more likely to prevent VT. However, rarely in patients, such medications will cause a cardiac arrest. Estimates of this risk are in the 1% range, but many physicians consider this to be too high of an estimate.

If several medications are tried, 50-70% of patients can be successfully treated and take the medications the rest of their lives. Careful follow up is required to be sure that these medications continue to be safe and effective. Amiodarone, the most potent of all heart rhythm medications is too risky for the vast majority of patients with idiopathic VT.

Ablation for idiopathic VT

Ablation is the option selected by the majority of patients. Reasons favoring ablation over other options include the following:

  • Patient Preference
  • Very Rapid VT
  • Poorly Tolerated VT
  • Patients Who Are Poor Candidates for Heart Rhythm Medications
  • Frequent Episodes of VT

Curative ablation for idiopathic VT involves doing a diagnostic procedure called an electrophysiology study or EPS first. It will determine the mechanism of the VT. Then the location of the origin of the VT is determined in an intracardiac mapping procedure. Usually a special three-dimensional mapping system is used in this procedure for precise localization of the source of the VT. Usually women have VT originating from the right ventricular outflow tract just below the pulmonic valve. Men may have VT from this location or from the fascicles of the left ventricle. Once the site of origin of the VT is located by identifying the earliest site of ventricular activation, special entrainment pacing maneuvers can sometimes be performed to prove that this is the correct site. If the VT cannot be induced at all then pacing the ventricle and recording an ECG for comparison with the ECG of the spontaneous VT can be used. Finally, ablative energy is then used to create a focal lesion that hopefully includes the VT focus or critical reentrant pathway. The lesions are small enough so as not to interfere with cardiac function. Then the heart is stimulated again to be sure that VT is no longer inducible. The whole procedure typically takes about 4 hours.

Outcome of VT ablation

The chance of ending the procedure with no VT inducible is at least 90% in experienced EP labs. The risk of the procedure in experienced hands is about 1%. The risks are slightly higher if the VT arises from the left ventricle. In one retrospective review of many published series, the risk of a thromboembolic complication was almost 3% for ablation in the left ventricle (2). Possible risks include minor events such as bleeding, infection, pain, nausea/vomiting, etc. More serious side effects include stroke, perforation of the heart, myocardial infarction, complete heart block requiring a permanent pacemaker, damage to heart valves, damage to blood vessels/nerves requiring an extended hospital stay, open-heart surgery, or even death.

Recurrence of VT

VT may recur in about 10% of patients. Early recurrences (usually less than 6-12 months) usually mean a recurrence of the original cause of the VT whereas later recurrences may signal a new focus or reentrant pathway. Options for patients with recurrence include the three original options:

  • Living with the VT (no therapy)
  • Taking heart rhythm medications
  • Repeat Ablation

Since most patients have a reasonable experience with their first ablation, the most common choice is repeat ablation at our institution.

Types of ablation

Most ablations for idiopathic VT are done with RF energy, which burns the origin of the VT. Cryoablation has been used for ablation of idiopathic VT to a limited extent. Possible advantages of cryoablation include the following:

  1. No painful sensation if the patient is awake
  2. Less irritation of the endocardium with thrombus formation
  3. Less chance of perforation
  4. Less chance of coronary artery damage if VT origin close to artery

There is one published series of ablation of right ventricular outflow tract VT. Success was achieved in 13 of 14 patients with no significant complications (3).

References

  1. 1. Reek S, Geller C, Schildhaus H etal. Feasibility of catheter cryoabaltion in normal ventricular myocardium and healed myocardial infarction. PACE. 2004; 27: 1530-1539
  2. 2. Zhou L, Keane D, Reed G et.al. Thromboembolic comlications of cardiac radiofrequency catheter ablation: a review of the reported incidence , pathogenesis and current research directions. Journal of Cardiovascular Electrophysiology. 1999; 10: 611-620.
  3. 3. Kurdizem K, Schneider HJ, Kuniss M, etal. Cryocatheter ablation of right ventricular outflow tract tachycardia. Journal of Cardiovascular Electrophysiology. 2005; 16: 366-369