ELECTROPHYSIOLOGY OF HEART.pptx

ELECTROPHYSIOLOGY OF HEART EXPLAINED BRIEFLY.

1. ELECTROPHYSIOLOGY OF HEART Dr Vijesha Soni, Pharm.D , Executive Clinical Pharmacist (Dept. of Pharmacology), Artemis Hospital, Gurugram.

2. What’s Cardiac Electrophysiology? Cardiac electrophysiology – study of elucidating, diagnosing, and treating the electrical activities of the heart . to assess arrhythmias , elucidate symptoms, evaluate abnormal electrocardiograms , assess risk of developing arrhythmias in the future, design treatment.

3. Normal heart An electrical impulse stimulates the heart muscle to contract. The normal electrical conduction starts in the sino -atrial (SA) node sending an impulse through the atria to the atrio -ventricular (AV) node, which is the relay station of the heart. It sends the electrical impulses to the ventricles.

4. The cardiac action potential The cardiac action potential, the basic unit of electrical activity in the heart, produces cardiac contractions. Cardiac myocytes , like other types of muscle cells, have a negative potential difference (-90 mV) at rest between the cell membrane and extra-cellular space ( ie , they are polarized). Under the influence of trigger events, potassium, sodium, and calcium ions cross the cell membrane , thereby generating discrete ion currents

5. Phases of cardiac action potential Divided into 5: Phase 0 (Opening of Na+ channels) Phase 1 (Opening of K+ channels) Phase 2 (Opening of Ca++ channels) Phase 3 (Opening of K+ channels) Phase 4 (Return to resting membrane potential)

6. Phase 0 Also known as “ rapid depolarization phase” Resting membrane potential in a myocardial cell is -90 mV With opening of Na+ channels  rapid influx of sodium ions into myocardial cells  depolarization occurs  Phase 0 begins.

7. Phase 1 Inactivation of sodium channels Activation/opening of potassium channels Action potential reduces. Slight downward deflection of action potential.

8. Phase 2 Also known as “ plateau phase ” In this phase  calcium channels get opened In this phase: Inward movement of calcium ions Outward movement of potassium ions. Since there is a balance between inward movement of calcium & outward movement of potassium  this phase is also known as “plateau phase”.

9. Phase 3 In this phase: Calcium channels close Potassium channels still remain open Due to above changes  repolarization occurs When membrane potential reaches -80 to -85 mV  K+ channels close.

10. Phase 4 Also known as “ Resting Membrane Potential”(RMP) Associated with diastole Certain myocardial cells  have potential to undergo spontaneous depolarization  generate action potential without any stimulus (automaticity) Spontaneous depolarization  fastest in SA node  hence it is also known as “pacemaker” From SA node  electrical activity begins  propagates to the rest of the heart.