3Heart_ppt.ppt
- 1. The Human Heart The heart is a muscle about the size of your fist. weighs approximately one pound. is located behind and slightly to the left of the breastbone. pumps about 5 quarts (4.7 liters) of blood every minute, or 1800 gallons (6768 liters) of blood every day.
- 2. Function of Heart The function of the heart is to circulate blood throughout the body. Pumping blood through the lungs removes carbon dioxide and refreshes the blood with oxygen. The oxygenated blood is pumped to the body to provide oxygen and nutrients and to remove waste products.
- 3. Contd... A healthy heart beats steadily and rhythmically at a rate of about 60 to 100 beats per minute when at rest (normal sinus rhythm). During strenuous exercise, the heart can increase the amount of blood it pumps up to four times the amount it pumps at rest, within only a matter of seconds.
- 4. Stucture of heart The heart’s structure has four chambers with one-way flaps called valves. The atria are the upper chambers and they receive blood that is being returned to the heart.
- 5. Contd… Right atrium receives blood with little oxygen because the blood has already circulated throughout the body delivering oxygen and nutrients. The left atrium fills with newly oxygenated blood returning from the lungs. When the atria pump (contract), they push the blood through valves (tricuspid and mitral) into the relaxed ventricles.
- 6. Contd… When the ventricles contract, the right ventricle pumps blood through the pulmonary valve into the lungs. The left ventricle pumps blood through the aortic valve to the body, including the heart (through coronary arteries). This continuous cycle of synchronized contractions is driven by the heart’s electrical system
- 7. Electrical System of Heart The heart's electrical system causes the heart to beat. controls the heart rate (the number of beats per minute). has (conduction pathways) that carry the electrical signals throughout the lower heart chambers (ventricles) for each heartbeat
- 8. Flow of electricity within the heart In a healthy heart, each heartbeat begins in the sinus node, which is located in the right atrium. The electrical signal from the sinus node (SA node) starts an electrical chain reaction that spreads across both atria, much like ripples on the calm surface of a pond. This causes the atria to contract and pump blood into the ventricles.
- 9. Contd… This electrical chain reaction continues from the atria through an area between the atria and ventricles called the atrioventricular (AV node or AV junction). The AV node connects to conduction pathways that relay the signal to the ventricles.
- 10. Contd… The AV node acts as an electrical gateway to the ventricles. The conduction pathways deliver the signals to the ventricles and the ventricles pump blood to the body.
- 11. Contd… An irregularity in the heart’s electrical system is called an arrhythmia, or heart rhythm disorder. Rhythm disorders can cause the heart to beat too slowly (bradycardia) or too fast (tachycardia).
- 12. The electrocardiogram An electrocardiogram (ECG) is a graphic produced by an electrocardiograph, which records the electrical voltage in the heart in the form of a continuous strip graph. It is the prime tool in cardiac electrophysiology Has a prime function in screening and diagnosis of cardiovascular diseases.
- 13. Lead Placement for ECG Leads I, II and III are measured over the limbs: I is from the right to the left arm, II is from the right arm to the left leg and III is from the left arm to the left leg. From this, the imaginary point V is constructed, which is located centrally in the chest above the heart. The other nine leads are derived from potential between this point and the three limb leads (aVR, aVL and aVF) and the six precordial leads (V1-6).
- 14. A Typical ECG Wave segment
- 15. Recording of ECG
- 16. Understanding ECG The P wave is the electrical signature atrial contraction. The QRS complex corresponds to theAtrial repolarization and ventricular depolarization The T wave represents the repolarization of the ventricles
- 17. Clinically Important Features The QT interval is measured from the beginning of the QRS complex to the end of the T wave. A normal QT interval is usually about 0.40 seconds. The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex. It is usually 0.12 to 0.20 seconds. RR interval is measured from the R-peak of one QRS complex to the next QRS complex’s R- peak.
- 18. Normal values Amplitudes P wave 0.25 mV R wave 1.60 mV Q wave 25% of R wave T wave 0.1 to 0.5 mV Durations P-R interval 0.12 to 0.2 sec Q-T interval 0.35 to 0.44 sec S-T segment 0.05 to 0.15 sec P wv interval 0.11 sec QRS interval 0.09 sec