Paroxysmal ventricular tachycardia (PVT) is a heart rhythm disorder, or arrhythmia, that originates in the lower chambers of the heart (ventricles). It involves a rapid, abnormal heart rate caused by a malfunction in the heart’s electrical system. The condition is defined by its sudden, intermittent nature, which often complicates diagnosis.
Defining Paroxysmal Ventricular Tachycardia
Paroxysmal ventricular tachycardia (PVT) is an electrical instability arising within the ventricles. Ventricular tachycardia (VT) refers to a rapid heart rhythm originating below the bundle of His, often exceeding 100 beats per minute. This rapid rate compromises circulation by reducing the heart’s ability to fill with blood between beats. The term “paroxysmal” means the episode spontaneously starts and stops, distinguishing it from sustained VT, which requires intervention to terminate. PVT episodes can last from seconds to hours before the heart reverts to a normal rhythm.
Mechanism of PVT
The underlying mechanism for PVT is frequently a re-entry circuit, which is an electrical short circuit within the ventricular muscle. Instead of traveling a precise pathway, the impulse gets caught in a self-perpetuating loop, continuously restimulating the tissue. This rapid electrical activity overrides the heart’s natural pacemaker, causing disorganized ventricular contractions. These contractions prevent the lower chambers from effectively pumping blood.
Recognizing the Signs and Triggers
Individuals experiencing PVT often feel a sudden onset of a racing heart, known as palpitations. Heart rates during an episode can exceed 200 beats per minute, causing significant physical distress. Other common symptoms include lightheadedness or dizziness, resulting from the temporary drop in blood pressure due to inefficient pumping. Shortness of breath and chest discomfort may also occur if the rapid rate prevents oxygen-rich blood from reaching the heart muscle. In severe or extended cases, the lack of effective circulation can lead to syncope, or fainting. Between episodes, the individual’s heart rhythm is typically normal.
Common Triggers
While PVT can occur without apparent cause, certain factors increase the likelihood of an episode. Physical or emotional stress and intense exercise are common triggers, as they increase adrenaline release, stimulating the heart. Underlying structural heart disease, such as coronary artery disease, heart failure, or scar tissue from a previous heart attack, can also predispose an individual to PVT. Additionally, stimulants like excessive caffeine, alcohol, and certain prescription or over-the-counter medications may trigger episodes.
Diagnostic Procedures
Confirming a diagnosis of PVT is challenging due to its intermittent nature. The primary diagnostic tool is the electrocardiogram (ECG), but a standard, in-office ECG is only useful if performed during an episode. Since episodes are unpredictable, ambulatory monitoring devices are necessary to capture the arrhythmia.
Ambulatory Monitoring
A Holter monitor is a portable ECG device worn continuously for 24 to 48 hours. For less frequent episodes, an event recorder is used, which the patient activates only when symptoms occur. For rare episodes, an implantable loop recorder, a small device placed beneath the skin, can monitor the heart rhythm for up to three years.
Electrophysiology (EP) Study
Once PVT is confirmed, an electrophysiology (EP) study may be performed to understand the precise mechanism and location of the electrical malfunction. This invasive procedure involves guiding specialized catheters into the heart through blood vessels. These catheters map the heart’s electrical activity and can intentionally trigger PVT in a controlled setting. This detailed mapping pinpoints the exact origin of the re-entry circuit, which is necessary before planning intervention.
Management and Treatment Approaches
Management of PVT is divided into acute treatment for ongoing episodes and long-term prevention strategies. For acute episodes involving severe symptoms or hemodynamic instability, immediate intervention is necessary to restore a normal rhythm. This may involve electrical cardioversion or the intravenous administration of antiarrhythmic medications like amiodarone or lidocaine.
Long-Term Prevention
Long-term management often involves antiarrhythmic medications to suppress abnormal electrical activity. Beta-blockers or calcium channel blockers may also be used to slow the heart rate and reduce muscle excitability. The most definitive treatment for recurrent, symptomatic PVT is catheter ablation.
Catheter Ablation and ICDs
During catheter ablation, the specific area identified by the EP study as the source of the re-entry circuit is targeted. Radiofrequency energy or cryotherapy is delivered through the catheter to create a small scar, destroying the misfiring tissue and permanently blocking the abnormal electrical pathway. For patients at high risk for dangerous rhythms, such as ventricular fibrillation, an Implantable Cardioverter-Defibrillator (ICD) may be recommended. This surgically implanted device continuously monitors the heart and delivers a life-saving electrical shock if a life-threatening rapid rhythm is detected.