Exercise Related to ECG and Medications chapter 24 Exercise Related to ECG and Medications

Heart Chambers and Valves Reprinted from J.E. Donnelly, 1990, Living anatomy, 2nd ed. (Champaign, IL: Human Kinetics), 199. Reprinted by permission of Joeseph Donnelly.

Coronary Blood Vessels Reprinted from J.E. Donnelly, 1990, Living anatomy, 2nd ed. (Champaign, IL: Human Kinetics), 199. Reprinted by permission of Joeseph Donnelly.

Oxygen Use by the Heart The myocardium relies on ATP for contraction. In the heart, 40% of the muscle cells are mitochondria. Even at rest, the heart muscle extracts 75% of the O2 delivered to it.

Electrophysiology of the Heart At rest, the insides of heart muscle cells are negatively charged. When depolarized, the insides of the cells become positively charged. If a wave of depolarization travels toward a positive electrode on the ECG, an upward deflection occurs.

Steps in an ECG Cycle

Electrical Conduction System of the Heart

Parts of the Electrical System Sinoatrial Node: Atrioventricular Node:

HIS-Purkinje System His Bundle (start of the system) Right Bundle Branch Left Bundle Branch Purkinje fibers Rate:

Electrocardiogram Electrocardiogram (ECG)

ECG Complex Showing Time and Voltage Scales Adapted from M.J. Goldman, 1982, Principles of clinical electrocardiography, 11th ed. (Los Altos, CA: Appleton & Lange), with permission of The McGraw-Hill Companies.

R T P T Knowledge of electrocardiography (ECG) is essential in clinical exercise physiology. The 12-lead ECG is a vital component of the evaluation of heart function during the exercise test. P Q S P-R Q-T Arial depolarization Ventricular depolarization

ECG Wave Forms (continued) P wave: QRS complex: T wave:

RATE

Normal Sinus Rhythm .

Sinus Bradycardia

Sinus Tachycardia

First-Degree AV Block

Second-Degree AV Block Type I (Mobitz Type I, or Wenckebach)

Second-Degree AV Block Type II (Mobitz Type II)

Third-Degree AV Block

Premature Atrial Contractions

Atrial Flutter

Atrial Fibrillation

Premature Junctional Contractions (PJCs)

Premature Ventricular Contractions (PVCs)

Ventricular Tachycardia

Ventricular Fibrillation When there are no discernible P waves or QRS complexes, the heart contracts in a disorganized, quivering manner.

Myocardial Ischemia

Myocardial Infarction Reprinted, by permission, from E. Stein, 1992, Rapid analysis of electrocardiograms, 2nd ed. (Philadelphia, PA: Lea & Febiger), 150.

Cardiovascular Medications Beta-blockers Nitrates Calcium channel blockers Antiarrhythmic medications Digitalis (continued)

Cardiovascular Medications (continued) Antihypertensives Lipid-lowering agents Anticoagulants Nicotine patches and gums Bronchodilators