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                                                        CARDIAC   ARRHYTHMIAS

                                                              Andrew Ying-Siu Lee, MD,PhD.

       The heart will work normally if it beats normally.  When the electrophysiological function of the heart is abnormal,  the heart will have pulse or conduction disturbances leading to irregular heart beats, so called cardiac arrhythmias.

       The etiology of cardiac arrhythmias include:  congenital or acquired, primary or secondary, cardiogenic or non-cardiogenic, low risk or high risk factors.  Common arrhythmias are :-

(1)        ATRIAL FIBRILLATION :  Most common cardiac arrhythmia.  Mostly due to cardiogenic factors such as valvular heart disease, congenital heart disease, coronary artery disease, heart failure, hypertension, autoimmune disease, WPW syndrome, cardiomyopathies, myocarditis, pericarditis etc.  Secondary causes include: alcohol abuse, post operation, hypoglycemia, electrolyte imbalance, endocrine and metabolic diseases, infections etc.  Common symptoms include: palpitation, dyspnea, dizziness, cold sweating, pallor, chest discomfort, heart failure etc.  Atrial fibrillation may lead to cardiomegaly, impaired heart function and heart failure, thromboembolism, stroke etc.  Therapy of atrial fibrillation include antiarrhythmic agents and anticoagulants, cardioversion, electrophysiologic study and ablation, cardiac pacemaker and surgery.

(2)        SUPRAVENTRICULAR TACHYCARDIA :  Commonly occur in young people.  Mostly non-cardiogenic or congenital (WPW syndrome), and the prognosis is usually good.  If occurred in the aged,  then it is usually due to cardiogenic factors such as heart failure, coronary artery disease, cariomyopathies etc.  Supraventricular tachycardia usually is abrupt in onset and intermittent.  The precipitating factors include : infection, emotional disturbance, over-exercise, drugs etc.  Common symptoms include:  palpitation, chest discomfort, dizziness, cold sweating etc.  Therapy of supraventricular tachycardia include antiarrhythmic drugs, cardioversion,. Electrophysiologic study and ablation, and surgery.

(3)      VENTRICULAR ARRHYTHMIAS :  Common arrhythmia.  Cardiogenic causes include: mitral or tricuspid valve prolapse, coronary artery disease, valvular heart disease, hypertension, cardiomyopathies, myocarditis, congenital heart disease etc.  Secondary causes include:  post operation, endocrine and metabolic diseases, drugs, emotional disturbance, alcohol abuse, smoking etc.  Common symptoms include: palpitation, dizziness, fainting, dyspnea, chest discomfort, cold sweating, heart failure, shock, coma, sudden death etc.  Ventricular arrhythmias can be benign or malignant, depending on the severity of arrhythmias (such as ventricular tachycardia or fibrillation), frequency of occurrence, underlying heart diseases, hemodynamics and heart function.  Therapy of ventricular arrhythmias include antiarrhythmic agents, cardioversion, electrophysiologic studies and ablation, implantable cardiac defrillator, surgery.

(4)        HEART BLOCK :  Can be divided into first, second and third degree heart blocks.  Cardiogenic causes include: degeneration or fibrosis of heart conduction system, sick sinus disease, coronary artery disease, congenital heart disease, valvular heart disease, autoimmune disease, cardiomyopathies, myocarditis, post operation, endocrine and metabolic diseases such as thyroid diseases and diabetus mellutis, drugs etc.  Common symptoms include: palpitation, bradycardia and tachycardia, dizziness, fainting, chest discomfort, dyspnea, weakness, heart failure, syncope etc.  Therapy of heart block include medications, electrophysiologic studies, cardiac pacemakers.

The symptoms of cardiac arrhythmias can vary from mild palpitation to the fatal heart failure, shock, coma, sudden cardiac death.  The prognosis of cardiac arrhythmias depends on the underlying heart diseases, heart function, kinds and severity of arrhythmias, frequency of occurrence, persistency, other concurrent illnesses and complications.

Since the kinds and causes of cardiac arrhythmias are numerous, the diagnosis and therapy of cardiac arrhythmias are difficult.  Firstly, correct diagnosis of the kinds of arrhythmias, their severity, persistency, primary or secondary factors etc.  Secondly, explore and treat the underlying heart diseases.  Thirdly, correct use of antiarrhythmic drugs. Fourthly, explore, prevent and treat the precipitating factors and concurrent illnesses.  Fifthly, explore and treat the complications such as heart failure, thromboembolism, stroke etc. Sixthly, explore and correct the hemodynamics and heart function, and finally, explore and correct timing for implementing electrophysiologic studies and ablation, cardiac pacemaker or defibrillator, and surgery.  The patients should comply with doctors’ advice and instructions, regularly follow up examinations and medications.  Thereby,  patients may have better life quality by improving the severity and prognosis of cardiac arrhythmias, and heart function.