What is the relationship between Ventricular tachycardia (Vt) and cardiac beats?

From the Guidelines

Ventricular tachycardia (VT) should be immediately managed with electrical cardioversion if the patient is hemodynamically unstable, and with antiarrhythmic medications like amiodarone or procainamide if the patient is stable, according to the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1.

Key Considerations

• The diagnosis of VT can be challenging, and a 12-lead ECG obtained during tachycardia and during sinus rhythm may reveal the etiology of tachycardia 1.
• The presence of atrioventricular (AV) dissociation or fusion complexes provides the diagnosis of VT 1.
• Long-term management includes implantable cardioverter-defibrillators (ICDs) for patients with sustained VT, especially those with structural heart disease or reduced ejection fraction 1.

Management Options

• For unstable patients with VT, immediate electrical cardioversion with 100-200 joules is recommended.
• For stable patients, antiarrhythmic medications like amiodarone (150 mg IV over 10 minutes, followed by 1 mg/min infusion for 6 hours) or procainamide (20-50 mg/min until arrhythmia suppression, hypotension, QRS widening, or maximum dose of 17 mg/kg) can be used.
• Beta-blockers like metoprolol (25-100 mg twice daily) or carvedilol (3.125-25 mg twice daily) are often prescribed as maintenance therapy.

Importance of Prompt Recognition and Treatment

• VT can quickly deteriorate into ventricular fibrillation and cardiac arrest, making prompt recognition and treatment essential 1.
• The risk of ventricular tachyarrhythmias in patients with acute MI is highest at the time of presentation and declines over the hours and days that follow 1.

From the Research

Relationship between Vt and Beats

• The relationship between tidal volume (Vt) and heart rate (beats) has been studied in various contexts, including mechanical ventilation and exercise 2.
• During exercise, Vt and heart rate are modified in a matter of a few heart beats, while respiratory rate varies depending on the subject and the level of exercise 2.
• The correlation between heart rate and Vt is positive, while the correlation between heart rate and respiratory rate is negative 2.

Effects of Vt on Cardiovascular Parameters

• Increasing Vt can affect stroke volume variability, which is a dynamic index of ventricular function 3.
• Stroke volume variability is sensitive to increases in heart rate, but the effect of increasing heart rate is less pronounced compared to increasing Vt 3.
• The use of low Vt ventilation can minimize the progression of lung injury, but it may also induce patient-ventilator dyssynchrony 4, 5.

Mechanical Ventilation and Vt

• Mechanical ventilation is a life-support system used to ensure blood gas exchange and assist respiratory muscles 6.
• The use of mechanical ventilation can lead to negative physiological consequences, including hemodynamic changes, local and systemic inflammation, and lung injury 6.
• Optimizing mechanical ventilation parameters, including Vt, is crucial to minimize ventilator-induced lung injury (VILI) and promote personalized ventilation 6, 4, 5.