Dr. Sandhya Dhruvakumer 4/18/13
Dr. Dhruvakumer gave a talk entitled: “The Beat Goes On- Atrial Fibrillation, Pacemakers and Other Problems of the Heart”. She is a Cardiac Electro Physiologist at Stamford Hospital specializing in the electrical system of the heart. She started by describing how electricity flows through the heart and how it is controlled in part by the Sinus Node. The Sinus Node is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Essentially it is the body’s pacemaker.
She then talked about Arrhythmia, which is a condition where the heart starts beating too slow or too fast. If the heart is beating too slow a Pacemaker can be surgically installed near the front of the collarbone to correct the heart rate. If the heart is beating too fast medication can be used to slow it down. The symptoms of Arrhythmia include: palpitations-being aware of the heart beating, fainting, light headiness, and lack of energy. Arrhythmia can sometimes be detected by a simple EKG in the doctor’s office, but this only provides a 10 second sample which can easily miss the Arrhythmia. A better technique is inpatient cardiac telemetry where the patient is monitored for 24 hours. Finally the best technique is for the patient to wear a monitor for 2-4 weeks which transmits the heart rate in real time. If the heart rate is too slow a Pacemaker can be installed that will stimulate the heartbeat electrically by sending electrical pulses to the upper and lower chambers as is done by the Sinus Node. The wires pass thru the Vena Cava to the heart where they are screwed in to the surface. The Pacemaker battery can last 7 – 11 years. In contrast with the Pacemaker treating Arrhythmia, a Defibrillator is used to treat Ventricular Fibrillation of the heart. Ventricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them quiver rather than contract properly. Ventricular fibrillation is the most commonly identified arrhythmia in cardiac arrest patients. Ventricular fibrillation is a medical emergency that requires prompt interventions. If this arrhythmia continues for more than a few seconds, it will likely degenerate further into asystole or “flatline”. This condition results in cardiogenic shock and cessation of effective blood circulation. As a consequence, sudden cardiac death will result in a matter of minutes. The solution is to “shock” the heart with high voltages thru external paddles. A built in Defibrillator can sense the heart quivering and apply the shock automatically.
A related condition, affecting over 2 million people in the U.S. is Atrial Fibrillation. Atrial fibrillation is often associated with palpitations, fainting, chest pain, or congestive heart failure. In AF, the normal regular electrical impulses generated by the sinoatrial node are overwhelmed by disorganized electrical impulses usually originating in the roots of the pulmonary veins, leading to irregular conduction of impulses to the ventricles which generate the heartbeat. AF may occur in episodes lasting from minutes to days, or be permanent in nature. AF increases the risk of stroke due to pooling of the blood in the Atrium, causing clots to form which can go directly to the brain. The degree of stroke risk can be up to seven times that of the average population, depending on the presence of additional risk factors such as high blood pressure.
Atrial fibrillation may be treated with medications to either slow the heart rate to a normal range or revert the heart rhythm back to normal. Depending on the risk of stroke and systemic embolism, people with AF may use anticoagulants such as Coumadin which substantially reduces the risk of clotting but may increase the risk of major bleeding, mainly in geriatric patients. The problem with Coumadin is that it requires frequent blood checks to get the right dose. Some newer drugs like Pradaxa and Xarelto do not require regular blood testing, but there is no antidote for them if you start bleeding heavily as in an accident. The prevalence of AF in a population increases with age, with 8% of people over 80 having AF. Surgical solutions to prevent clotting involves sealing off the appendages in the Aortic Cavity where clots can form. Finally the latest surgical technique for AF is to prevent the pulmonary veins from being electrically connected to the heart resulting in the elimination of AF altogether.
During Q&A the following points were made:
1. Pacemakers make use of internal pulse detectors to measure the heart rate and make needed adjustments. Defibrillators use imbedded motion sensors to determine if the heart is quivering so as to apply an electrical shock.
2. AF is very strongly correlated with high blood pressure.
3. There is no fixed limit as to how low blood pressure can go. Many factors are involved depending upon the individual.
4. Heparin is not an outpatient medicine. It is only given with IV’s in a hospital setting. It is used to bridge the time needed for Coumadin to kick in, typically 2 or 3 days.
5. The Sinus Node can be disturbed by heart surgery resulting in a need for a Pacemaker.
6. A major cause of AT is stress in the body caused by excessive drinking, sleep apnea and other stress inducing lifestyles..
Thanks Brian for a great speaker.