Pulseless ventricular tachycardia (PVT) is a life-threatening heart rhythm disorder characterized by a very fast heartbeat originating from the lower chambers of the heart, known as ventricles. The heart beats too fast to pump enough blood to the body, causing a lack of pulse and low blood pressure. Immediate medical help is required to restore a normal heart rhythm.
This article will provide a comprehensive overview of pulseless ventricular tachycardia, including causes, symptoms, diagnosis, treatment options, and ways to prevent recurrence. Frequently asked questions will be answered to help patients and caregivers better understand and manage this condition.
What is Pulseless Ventricular Tachycardia?
Pulseless ventricular tachycardia (PVT) is a subtype of ventricular tachycardia (VT) where the heartbeat is so rapid that little or no blood is pumped to vital organs such as the brain and heart. It results in no pulse or very weak pulse that cannot be felt, low blood pressure and lack of adequate blood circulation.
In PVT, the heart beats at a rate of more than 100 beats per minute originating from the lower chambers called ventricles. The ventricles contract so forcefully and quickly that they fail to relax and refill with blood properly between contractions. This makes it impossible for the heart to effectively pump blood to the body.
Some key characteristics of pulseless ventricular tachycardia include:
- Heart rate of more than 100 beats per minute
- Absence of a detectable pulse
- Narrow QRS complex or wide QRS complex depending on origin
- Low blood pressure is often less than 80 mmHg
- Loss of consciousness if not treated promptly
PVT is considered a cardiac emergency that requires immediate resuscitation efforts to restore a normal rhythm and adequate blood flow to prevent death. The goal is to defibrillate the heart and provide compressions to maintain circulation until the heartbeat stabilizes.
Causes of Pulseless Ventricular Tachycardia
There are several factors that can trigger an episode of pulseless ventricular tachycardia by disrupting the heart’s normal rhythm. Some of the common causes of PVT include:
- Heart attack: Damage to heart muscle from a myocardial infarction can cause scarring that disrupts the heart’s electrical system and triggers arrhythmias.
- Hypoxia: Lack of adequate oxygen to the heart most commonly due to respiratory failure, drowning or cardiac arrest can provoke PVT.
- Hypokalemia: Abnormally low potassium levels in the blood known as hypokalemia predispose the heart to arrhythmias.
- Toxic ingestions: Recreational drugs, medication overdose or poisoning may directly affect the heart and lead to PVT.
- Cardiomyopathies: Diseases that weaken and enlarge the heart muscle such as dilated cardiomyopathy increase the risk.
- Congenital heart defects: People born with structural heart abnormalities have a higher likelihood of life-threatening rhythms.
- Viral infections: Some viral infections like myocarditis can cause transient inflammation in the heart and cause arrhythmias.
- Electrolyte imbalances: Disturbance in sodium, calcium and magnesium levels can destabilize the heartbeat.
- Idiopathic: Sometimes the trigger cannot be identified and the cause is considered idiopathic.
Identifying and addressing the underlying cause is crucial to prevent recurrences of PVT in future. Lifestyle changes and medications can help modify risk factors in many cases.
Symptoms of Pulseless ventricular Tachycardia
The hallmark symptoms of pulseless ventricular tachycardia are:
- Loss of consciousness: As blood pressure plummets due to ineffective pumping, the brain is deprived of oxygen leading to fainting or coma.
- Absence of pulse: Palpation of peripheral arteries like the carotid or femoral fails to detect a pulse as the heartbeat is too rapid.
- Hypotension: PVT results in very low blood pressure readings, often under 60 mmHg.
- Feeling of weakness: With decreased circulation from rapid heart rates, people may experience dizziness or feeling lightheaded prior to losing consciousness.
- Chest pain: The abnormal heart rhythms can cause a burning, pressure or tightness in the chest.
- Shortness of breath: Hypo-perfusion of lungs leads to respiratory distress and breathing difficulties.
- Cyanosis: Bluish discoloration of the skin, lips and nail beds occurs due to lack of oxygen carrying red blood cells.
Since PVT causes abrupt loss of circulation, other symptoms arise only after collapse and include cold sweat, pallor and involuntary bladder or bowel movements. Early signs are often non-specific like feeling unwell but it quickly progresses to life-threatening hemodynamic instability. Prompt medical assistance is necessary for survival.
Diagnosing Pulseless Ventricular Tachycardia
The diagnosis of pulseless ventricular tachycardia involves a combination of physical examination findings, medical history and diagnostic tests:
Physical exam: Initial assessment focuses on checking breathing, pulse, and response to determine if cardiopulmonary resuscitation (CPR) is needed. Later, cardiologist examines for signs of underlying heart disease.
Medical history: Details of present illness, past health issues, risk factors, medication and family history help identify triggers and assess recurrence risk.
12-lead ECG: Electrocardiogram shows characteristic wide QRS complexes and absence of P-waves confirming arrhythmia origin in ventricles during attack. It can also detect prior heart damage or inflammation.
Echocardiogram: Ultrasound of the heart muscle allows visualization of structural abnormalities, areas of poor pumping function, blood clots or valve issues that may have led to PVT.
Cardiac enzymes: Blood tests for troponin and CK-MB levels are done to rule out heart attack as a precipitating factor if elevation is seen post-resuscitation.
Electrophysiology study: This specialty test involves placing electrode catheters inside the heart to precisely map electrical activities and track stimulus conduction if the arrhythmia etiology is unclear.
Event monitor: This small portable device records periodic or continuous ECG over days to weeks to capture any arrhythmias on discharge from the hospital.
Advanced imaging, such as cardiac MRI and CT-angiogram, may be used selectively to better define abnormalities when the cause cannot be identified otherwise. A cardiologist closely analyzes all results to determine the appropriate treatment approach.
Treatment of Pulseless Ventricular Tachycardia
The immediate emergency treatment of pulseless ventricular tachycardia focuses on restoring blood circulation through cardiopulmonary resuscitation and defibrillation. Further long-term management addresses underlying triggers and prevents complications.
Cardiopulmonary resuscitation (CPR)
Chest compressions are started immediately to manually pump the heart while rescuers prepare the defibrillator. Compressions at a rate of 100-120/minute are critical to circulate oxygenated blood in major organs.
Defibrillation
A defibrillator delivers a controlled electric shock called countershock through pads placed on patient’s chest. This depolarizes a critical mass of heart muscle cells simultaneously to interrupt the chaotic rhythm and provide opportunity for normal sinus rhythm to resume on its own.
Emergency medications
Drugs like epinephrine, amiodarone, lidocaine may be given during cardiac arrest to help improve the effectiveness of CPR and shock or stabilize the heart if rousable rhythm observed after initial shocks.
Post-resuscitation care
After return of spontaneous circulation, patients require intensive care for cardiac monitoring, treatment of causes, prevention of complications and recovery support.
Implantable cardioverter defibrillator (ICD)
For survivors at high risk of recurrent PVT due to structural heart disease, an ICD device placed under the skin continuously monitors heart rhythm and treats lethal arrhythmias instantly with shocks if needed.
Catheter ablation
An electrophysiology procedure where targeted areas in the heart are ablated or destroyed using radiofrequency energy or freezing to isolate and interrupt abnormal conduction pathways. It offers cure for some arrhythmia causes.
Medications
Antiarrhythmic drugs like amiodarone, mexiletine help suppress recurrent episodes but have potential side effects requiring close monitoring. Drugs addressing triggers like beta-blockers are also used.
The aims of long-term management are stabilizing cardiac function, prevention of future attacks, lifestyle modifications, control of contributors and prompt defibrillation if arrhythmia recurs while awaiting transplantation if needed. Early intervention improves outcomes.
Preventing Recurrence of Pulseless Ventricular Tachycardia
Once an episode of pulseless ventricular tachycardia is stabilized, efforts focus on minimizing the risk of repeat attacks through a combination of medical, device-based and lifestyle modifications:
- Compliance with medications as directed by cardiologist
- Wearing a medical identification to alert rescuers of heart condition
- Maintaining normal electrolyte and mineral balance
- Optimizing control of underlying conditions like heart failure
- Treating viral or bacterial infections promptly
- Avoiding stimulants that can trigger arrhythmias
- Limiting alcohol and recreational drug consumption
- Implantable cardiac defibrillator placement if high-risk
- Obtaining influenza and pneumococcal vaccines
- Quitting smoking and minimizing other cardiovascular risks
- Following a Mediterranean diet rich in fruits and vegetables
- Managing hypertension, diabetes and obesity
- Addressing psychosocial stress through relaxation techniques
- Consulting doctor before major surgeries or procedures
Early recognition of warning signs and seeking medical care promptly helps terminate arrhythmias in initial stages before progressing to pulseless rhythms. A heart-healthy lifestyle combined with proactive management of modifiable factors reduces long-term complications.
FAQs About Pulseless Ventricular Tachycardia
Here are answers to some commonly asked questions about pulseless ventricular tachycardia:
What is the prognosis after PVT?
The outcome depends on how quickly resuscitation begins and underlying cardiac health. With prompt CPR and defibrillation, survival rates are around 50-70%. Recurrences are common in structural heart disease without medical treatment or ICD.
Can PVT happen without warning?
In many cases, PVT develops suddenly without apparent symptoms. But some experience vague sensations like palpitations, dizziness, chest pain before collapse. Recognizing and reporting these promptly helps prevent progression to pulseless rhythms.
How can bystander CPR help?
Early initiation of chest compressions during cardiac arrest is critical to circulate oxygenated blood until defibrillation. Compressions increase survival odds 2-3 times compared to no bystander assistance. All rescuers should be trained in CPR.
What activities are restricted after PVT?
High-risk activities involving risks of falling, drowning, or trauma are limited until stabilized on an optimal medical regimen. Contact sports may require clearance. Driving needs to be discussed with a cardiologist based on recurrence risk and response to treatment.
Can PVT occur during sleep?
Arrhythmias can occur anytime, but the risk is higher at night for those with structural heart issues or sleep apnea. Make sure to use pillows appropriately and consider a bed partner who can provide help if breathing difficulties arise during sleep.
What follow-up tests are required?
Periodic cardiology checkups involving history, exam, ECG, and echocardiogram monitor for any signs of disease progression or the effectiveness of treatment. Device interrogations, Holter monitoring, and repeat ablation may be needed based on individual circumstances.
How much advance will research bring?
Ongoing research focuses on improving understanding of triggers, enhanced defibrillation techniques, more targetable ablation approaches, and the development of future gene therapies or stem cell applications. Meanwhile, preventive strategies have substantially reduced mortality over the past decades.
Wrapping Up
In summary, pulseless electrical activity denotes a life-threatening scenario where cardiac electrical activity is present on ECG, but the heart muscle fails to contract and pump blood adequately. Untreated PEA leads to rapid progression to full cardiac arrest. Prompt identification of PEA based on absent pulses despite synchronized electrical activity on monitoring, followed by immediate initiation of high-quality chest compressions and treatment of reversible causes in line with resuscitation guidelines, offers the best chance for resuming spontaneous circulation and survival. While the outcome is influenced strongly by causes and quality of care provided, early recognition and management optimize recovery. Continued efforts focus on preventing conditions predisposing to circulatory collapse and guiding at-risk patients against deterioration through vigilant surveillance. With timely, evidence-based treatment following established protocols, more lives can be saved in the setting of a PEA cardiac emergency.
