Tachycardia (fast heart rates)

Do you experience Fast heart rates (Tachycardias)?

 

What do the patients complain of?

 

The patients tend to complain of episodes of palpitations due to fast heart rates. Some patients may feel giddy or have  episodes of fainting if the heart rates are too fast.

 

How is this condition diagnosed?

The condition can be diagnosed by a electrocardiogram (ECG) which reveals the fast heart rate. Some patients may need to undergo EP study to diagnose this condition.

What are the causes of Fast heart rates?

These can be due to various causes, however, the common one seen are SVT (supra-ventricular tachycardia), AF (atrial fibrillation) and VT/VF (ventricular tachycardia/ fibrillation).

  • SVT (Supra-Ventricular Tachycardia):  These are caused by the presence of an extra electrical connection between the upper and lower chambers. These patients experience intermittent fast heart rates associated with palpitations and lightheadness. The episodes can be highly distressing and limit one’s activities. They can be easily controlled with medications. However, with the advent of new technology, it has become easier to get rid of them and cure the patient of the fast heart rates. The procedure is called EP (electrophysiology) study and is carried out by inserting small catheters via one’s groin upto the heart. The heart is then stimulated to start the fast heart rate and the location of the extra connection is studied. The pathway can be burnt (ablated) by radiofrequency energy in a controlled manner with the help of catheters. These procedures have a good success rate (> 90%) and take around 2-3 hours. The patient can be mobilized after few hours and discharged the next day.

 

  • Atrial fibrillation: This is a disease of the elderly in which the upper chambers (atria) beat at extremely fast rates (400-750 beats/minute). Thus there is no effective pumping of the upper chamber, causing blood to stagnate and form clots which can cause strokes in high risk individuals. These patients need to be treated with drugs called blood thinners to reduce the risk of stroke. In addition, drug therapy is required to prevent the lower chambers from going fast which can be very distressing to the patient or life threatening. Ablation therapy can be offered in some patients in the early form of the disease. The procedure lasts 4-6 hours and are done through the groin. The chances of recurrence are high (around 30%)

 

  • VT (ventricular tachycardia): These are life threatening and are responsible for sudden cardiac deaths. Most of the patients who suffer from these either have blocks in their blood supply to the heart (have suffered heart attacks before) or have low pumping function of the heart. These patients can be controlled by oral medications. However, devices called Defibrillators are implanted to treat future episodes and to reduce the death rate in patients with heart attacks and poor heart function.  These are implanted just like pacemakers except that they have the additional function to detect and shock these dangerous rhythms. In patients with poor heart functions, an extra wire (lead) is placed on the left side of the heart to improve the heart function.

Devices for Heart Failure

Devices for Heart Failure:

 

There are 2 devices which can be used in HF treatments (1) Cardiac Resynchronization Therapy and (2) Implantable Cardiac Defibrillator

 

(I) Cardiac Resynchronization Therapy:

The heart is made of 2 upper chambers called atria and 2 lower chambers called ventricles. An electrical system controls the synchronized pumping action of these chambers. The atria contract first followed by the 2 ventricles. The 2 ventricles contracts simultaneously to as to ensure optimal pumping of blood to the body and lungs. However this synchronized contraction (Synchrony) is lost between the atria and the ventricles and also between the 2 ventricles. This dys-synchrony leads to further less effective contraction of the heart thereby reducing thereby aggravating the heart failure. This Dys-synchrony can be easily diagnosed by the Physician with the help of the electrocardiogram and the echocardiogram.
CRT is designed to correct this dys-synchrony between the upper and lower chambers of the heart and also between the 2 lower chambers. This ensures simultaneous contraction of the 2 lower chambers thereby improving the contractions. In this procedure, a pacemaker (the size of a pager) is implanted just below the skin in the upper chest region and 3 wires (leads) are inserted into the heart to deliver electrical therapy. The 3 leads are positioned in the right upper, right lower chambers and the left lower chambers. The CRT device simultaneously stimulates the left and right ventricles and restores a coordinated, or “synchronous,” squeezing pattern. This reduces the electrical delay and results in a more coordinated and effective heart beat.

Who needs the CRT?
According to the Heart Rhythm Society, the ideal candidate for a CRT device is someone with:

  1. Moderate to severe heart failure symptoms, despite lifestyle changes and medication
  2. A weakened and enlarged heart muscle
  3. A significant electrical delay in the lower pumping chambers.

How effective is CRT?

There have been around 8-9 clinical trials involving around 5000 patients. Clinical studies demonstrate modest improvements in exercise tolerance, heart failure severity, and quality of life in most patients. Almost two-third of the patients implanted with the device benefit in their symptomatic status and also have decrease in the number of hospitalizations over the next few years. Improvement may happen quickly, but sometimes it can take several months.

(II). Implantable Cardiac Defibrillators (ICD)

ICD is a device designed to shock the heart out of a dangerous life threatening rhythm. The device is similar to the pacemaker and is the size of a pager. It is implanted below the skin in the upper chest and is then connected to a wire (lead) which monitors the heart rhythm 24 hours. Whenever it detects a dangerous heart rhythm, it delivers an internal shock to the heart and restores the normal rhythm.

Who needs ICD? Who is at risk of developing dangerous heart rhythm?

Dangerous heart rhythms can cause Sudden Cardiac Arrest which can cause instant death. Patients most at risk are those with compromised heart function (Ejection fraction < 35%). These patients if symptomatic need to undergo an ICD implantation so as to reduce their risk of dying from sudden cardiac arrests.

How effective is ICD?

There have been around 6 clinical trials involving around 3000 patients. Clinical studies demonstrate modest reduction in the death rates due to sudden cardiac arrest and have been life-saving in the majority of the patients.

Summary:

Patients with heart failure are at risk of dying from progressive heart failure and sudden cardiac arrest. This can be now corrected and treated effectively by implanting devices (namely CRT and ICD respectively). However, these patients need to be carefully evaluated and selected by the cardiologist before undergoing these procedures so as to ensure maximum benefit.