+ Health and Sciences +

SA (Sinoatrial) node is the pacemaker of human heart.AV (Atrio-ventricular) node is the conduction junction between Atria and ventricles.It transmits the impulses originating in the SA node (present on right atrium) to the ventricles.Any conductional defects in the AV node may cause ventricular tachyarrhythmias and ventricular failure. In any suspected case of conduction disturbances, the physician must assess The site of block The risk of turning into a complete block The probability that a subsidiary escape rhythm develops distal to the block. If the escape rhythm pace maker is in the HIS bundle, the ectopic impulse is stable and the rate is usually 40 - 60 beats/min.QRS complex is normal in duration. If ectopic rhythm is present in HIS-Purkenjee system, ectopic rhythm is unstable and rate is usually 25 - 45 beats/mins.QRS complex id prolonged. Etiology : Seen in following conditions- Chronic athlets have hypervagal stimulation.Mobitz type two AV conduction block is mostly seen in th

Systemic illness : Cardiac manifestation - Skeletal mucle Dystrophy : Cardiomyopathy, atrial fibrillations, Mitral stenosis. Stroke Mitral stenosis, Atrial fibrillation. Hemochromatosis : Myocardial Infarction, Restrictive heart disease. Congenital deafness : Prolonged QT Interval, arrhythmias. Raynaud's disease : Pulmonary hypertension, Coronary vasospasm. Conective tissue Disorder (Marfan's Syndrome) : Aortic aneurysm, Mitral valve prolapse. Hyperthyroidism : Atrial Fibrillation, Heart failure. Hypothyroidism : Coronary artery disease, pericardial effusion. Rheumatoid arthritis : Pericarditis, Aortic valve disease. Scleroderma : Cor pulmonale, pericarditis, Myocardial fibrosis. SLE : Pericarditis, Vlavulitis, Myocarditis. Sarcoidosis : Arrhythmias, Cardiomyopathy. Lyme Disease : Unexplained fluctuating AV block.

Right Atrial Overload - Leads to Increase in P wave amplitute (>2.5 mm) Left Atrial Overload - Produces biphasic P wave in V1 with a broad negative component or a broad notched P wave in 1 or more limb leads.(This pattern may also occur in left atrial conduction delays.) Right ventricular Pressure overload - Characterised by tall R wave in V1 with right axis deviation.St depression and T wave inversion in right to mideprecordial leads ( Ventricular strain pattern : attributed to repolarisation abnormalities in hypertrophied muscle.) are also often present.There may be qR pattern in V1 or V3R Right Ventricular Volume overload - is associated with complete or incomplete right bundle branch block with rightward QRS axis deviation. Acute Cor Pulmonale - Most commonly due to pulmonary embolism. QRS axis shifts to right.S1Q3T3 pattern (prominence of S wave in lead 1, Q wave in lead 3 and inversion of T wave in lead 3. Chronic Cor Pulmonale - Mostly due to pbstructive lung disease.