Ventricular tachycardia: Clinical sciences

Ventricular tachycardia, also known as VT or V-tach, is a wide-complex tachycardia originating from an ectopic ventricular pacemaker, often in the setting of myocardial ischemia or structural heart disease.

Ventricular tachycardia is a poorly perfusing rhythm, so patients may present with or without a pulse. It often presents with hemodynamic instability, which requires emergent intervention to restore a perfusing rhythm.

Bear in mind that some patients with VT might be hemodynamically stable upon presentation, but they’re at risk of becoming unstable quickly and with no warning, potentially even deteriorating to ventricular fibrillation, so they’re still managed emergently.

Now, based on duration, VT can be classified as non-sustained, which lasts less than 30 seconds, or sustained, which lasts more than 30 seconds. Additionally, based on the pattern of QRS complexes, VT can be described as monomorphic or polymorphic.

Now, if an individual presents with signs or symptoms of VT, you should first perform an ABCDE assessment. These patients will generally be unstable, so begin acute management. Stabilize their airway, breathing, and circulation. Next, obtain IV access, attach a cardiac rhythm monitor, and provide supplemental oxygen if they’re hypoxemic.

Here’s a high-yield fact! While providing acute management, it’s also important to look for reversible causes, which can be remembered as the 5 H's and T's. The H’s include Hypoxia, Hypothermia, Hypovolemia, Hydrogen ions for acidosis, and Hyper- or Hypokalemia; while the T’s include Toxins, cardiac Tamponade, Thrombosis for myocardial infarction, Thrombosis again for pulmonary embolism, and Tension pneumothorax. Next, assess for signs of VT on the cardiac rhythm monitor.

Signs of VT include a heart rate above 150 beats per minute, QRS complex width of 140 milliseconds or greater, and the presence of AV dissociation, which means there’s no clear relationship between the P waves and QRS complexes.

If there are no signs of VT, consider an alternative diagnosis. On the other hand, if all signs are present, diagnose ventricular tachycardia. Now, after diagnosing VT, you need to assess the duration.

Now a clinical pearl! All patients with pulseless VT must be treated with immediate defibrillation, while patients with a pulse can be treated with antiarrhythmics like amiodarone or procainamide.

If the episode lasts less than 30 seconds, it’s called non-sustained VT. In this case, the VT terminates spontaneously and a perfusing rhythm is restored, which generally means your patient is now stable. The next step is to perform a focused history and physical exam; obtain a 12-lead ECG; order labs, including a BMP and cardiac enzymes; and finally, obtain a transthoracic echocardiogram or TTE.

If your patient reports anginal chest pain, ECG shows ST or T changes, and labs reveal elevated cardiac enzymes, diagnose Acute Coronary Syndrome. Management typically requires reperfusion therapy, which can be either pharmacological, or mechanical, which involves percutaneous coronary intervention.

On the other hand, if your patient reports exertional dyspnea, exam reveals peripheral edema, and TTE shows systolic or diastolic dysfunction, diagnose structural heart disease.

In this case, treat the underlying cause, and consider placing an implantable cardioverter defibrillator if the left ventricular ejection fraction is under 35%.

Alternatively, if your patient reports palpitations, the ECG shows U waves, and labs reveal low potassium, diagnose hypokalemia and administer intravenous potassium.

Finally, if history reveals no chest pain or exertional dyspnea, ECG shows no changes, labs are normal, and TTE shows no evidence of structural heart disease, diagnose idiopathic VT. This doesn’t require treatment unless it becomes recurrent, in which case beta-blockers are the preferred treatment.

Alright, now let’s take a look at patients with VT that lasts more than 30 seconds, called sustained VT. In these individuals, first, you need to assess the QRS morphology.

If the QRS complexes look similar from beat to beat, diagnose monomorphic VT.

Follow ACLS guidelines to terminate the dangerous rhythm. These might include the Pulseless Arrest guideline if no pulse is detectable, or the Tachycardia with a Pulse guideline if a pulse is present.

Once the VT terminates and a perfusing rhythm is restored, your patient will generally become more stable, so perform a focused H&P, and obtain a 12-lead ECG and TTE.

If your patient has a history of previous myocardial infarction, ECG reveals pathologic Q waves, and TTE shows an area of myocardial scar, diagnose ischemic cardiomyopathy. These patients are at high risk of recurrent VT, so consider placing an implantable cardioverter defibrillator.