Tachycardia

Measuring the heart rate is one of the key diagnostic methods in identifying a cardiac condition. The normal heart rate of an individual is 60 – 100 when the cardiac muscle is in resting condition. Tachycardia is a condition in which the normal heart rate of a person increases and the entire rhythmic contraction of the heart muscle is affected. Sinus Tachycardia is usually a response of the cardiac muscle to exercise, stress or underlying illness. Although there are many forms of tachycardia, it is broadly classified into two predominant types depending upon the chambers of the heart.

Atrial Tachycardia

The conditions are associated with the atrial chambers or the upper chambers of the heart. They are further classified.

Atrial Fibrillation: In this condition, the cardiac electrical conductivity is rapid and irregular leading to irregular heart muscle contraction. The rapid contractions thus produced affect the ventricles. This type of cardiac disease is associated with hypertension and hyperthyroidism. Another associated condition related to atrial fibrillation is atrial flutter.

Supra Ventricular Tachycardia: This condition is caused above the ventricles causing abnormal cardiac conduction leading to superimposed or overlapped signals. It is related to AV node abnormalities in which the cardiac signal arriving at the AV node is split into two with the rebound of one signal to the atria and one signal to the ventricle. These conditions can also lead to Wolf Parkinson's disease which emphasizes the deflected pathway of the arriving signal.

Ventricular Tachycardia

Ventricular tachycardia is a serious cardiac condition. Ventricular fibrillation and associated tachycardia is because of rapid and uncontrolled emergence of cardiac electrical signals leading to extreme arrhythmia and subsequent heart failure.

Risk factors

Cardiac diseases are predominantly caused because of stress or congenital deformities. In most cases obesity, alcohol, smoking and drug abuse have been the predominant sources of increased mortality because of cardiac attacks.

Diagnosis and Treatment

Cardiac conditions are detected with an ECG. The ECG reveals the cardiac conductivity in the four chambers of the heart. Altered patterns can be observed clearly in comparison with the normal graph generated by one cycle of cardiac conduction. Holter monitor, an advanced and portable device performing similar function is used on patients to monitor their cardiac activity for a period of 24 hours. Treatment methods usually include administration of beta-blockers to control arrhythmia and to prevent the occurrence of stroke. Vagus nerve maneuvers and defibrillation methods often help in the recovery of the heart muscle from rapid arrhythmia.

Cardiac event monitor

The cardiac event monitor is a small device that is used to record the electrical activity of the heart. The cardiac event monitoring test allows for on-demand heart monitoring outside the hospital/clinic settings when symptoms are noted by the patient as he/she goes through the normal routine. The information collected by a cardiac event monitor is often sent over the phone to a doctor's office, clinic or hospital. This helps the doctor choose a line of treatment to meet the specific needs and demands of the patients' condition. The cardiac event monitors are easy to use by people of all ages.

The cardiac event monitor is clipped to the waistband of the patient. The monitor is connected to a set of wires which are attached to two electrodes worn on the patient. The EKG electrodes are small sticky patches attached to the patient's chest. The monitor can be worn for up to 30 days. Normally cardiac event monitor is used to record an abnormal heart rhythm. The patient triggers the cardiac event monitor device when he first begins to feel signs of dizziness, weakness, lightheadedness and fluttering of the heart.

Loop recorder: This is a small device that is attached to the patient's chest with electrodes. The smallest type of pre-symptom event monitor is about the size of a pager. The event monitor device constantly records heartbeats. The patient presses a button on the monitor when any symptoms occur so that a permanent recording is made of the heart rhythm. The monitor also saves some information about how the patient's heart was beating before the save button was pressed. This is called pre symptom recording. This feature is especially useful to detect the patient's condition at the time the heart problems occur.

Event recorder: This is a small monitoring device that is used only when symptoms of the heart problems occur. It does not have any electrodes attached to the chest.

• The patient should ensure to keep the patches within the designated areas.
  
• The monitor batteries should be changed at the same time each day.
  
• A diary has to be kept handy to record the events.
  
• Transmitting of the recording can be done daily, weekly or whenever the patient feels symptoms that warrant immediate attention.
  
• If the findings indicate that immediate medical care is required, then the doctor has to be notified right away.
  

Cardiac Stress Test

A cardiac stress test aids in assessing how the heart can cope during exercise, especially when the body need for oxygen puts extra demands on the heart. A cardiac stress test is called a graded test or exercise tolerance test, exercise stress test or exercise electrocardiography. It helps to primarily evaluate the heart and vascular systems during the exercise. In fact, the American Heart Association has recommended the Cardiac stress test (EKG treadmill in particular) as the first choice to be tried on patients with medium risk of coronary heart disease and who exhibit certain risk factors of smoking, family history of coronary stenosis, high blood pressure, and high cholesterol.

• It helps to determine whether coronary arteries are clogged or blocked.
  
• To find the cause of chest pain.
  
• To assess the heart's capability after a heart attack or heart surgery.
  
• To discover the presence of any heart disease.
  
• To set limits on a person's exercise.
  
• To detect arrhythmia, that is extra heart beats, during the exercise.
  
• To assess the capacity of medicine used to control chest pain or extra beats during exercise.

The cardiac stress test can be done in a clinic or a hospital. The patient may be asked to exercise using a bicycle, treadmill or arm ergometer. The patient is attached to an ECG machine. The blood pressure cuff is placed on any one arm. The patient's heart is usually monitored using a 12 - lead EKG or ECG machine. A heart monitor may be used during and after exercise. After a baseline ECG is obtained, the patient begins to perform a low level of exercise, either by walking on a treadmill or pedaling on a stationary bicycle.

At each stage of the exercise, the pulse, the blood pressure and ECG are recorded along with any symptoms that the patient may be experiencing.

The level of exercise is gradually increased until the patient cannot keep up any longer because of fatigue or until symptoms like chest pain, shortness of breath or lightheadedness prevent further exercise. The goal of this stress test is to diagnose the presence or absence of coronary artery disease. In a sub maximal stress test, the patient exercises only until a pre-determined level of exercise is attained. These tests are used in patients with known coronary artery disease, to measure whether the patient can perform a specific level of exercise with relative safety.

The side effects of a cardiac stress test also include palpitation, chest pain, and shortness of breath, headache, nausea and fatigue. The hypertension caused by stress testing is always considered abnormal and it may lead to severe coronary disease. In stress tests, false positive results are not uncommon. There can be occasions when the patient's ECG changes could suggest ischemia, even in the absence of coronary artery disease. Similarly, in stress test, false negatives are also not uncommon. In some patients, no significant ECG changes will be seen even in the presence of coronary artery disease. Presently, a new concept called nuclear perfusion study is added to the stress test. This factor has helped to minimize the limitations and improve the diagnostic capability of stress tests.