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Cardio Vascular Anatomy & ECG
- 1. Cardio Vascular Anatomy & ECG Shibu Chacko
- 2. Anatomy of The Heart Left Atrium Right Atrium Right Ventricle Left Ventricle (3-4 times thicker than the right) Papillary Muscles Chordae Tendineae Mitral Valve Tricuspid Valve Septum
- 3. Venous blood leaves both the superior and inferior vena cava and enters the right atrium The atrium contracts forcing blood through the tricuspid valve, into the right ventricle
- 4. Once the right ventricle fills, it then contracts, forcing the tricuspid valve to close and the pulmonary valve to open. This permits the blood to enter the pulmonary artery. As the right ventricle relaxes, the pulmonary valve closes to prevent backflow In the lungs carbon dioxide is released and oxygen is picked up by the hemoglobin in the red blood cells This oxygenated blood travels via the four pulmonary veins into the left atrium
- 5. The left atrium then contracts, forcing blood past the mitral valve into the left ventricle The left ventricle then contracts, closing the mitral valve and opening the aortic valve forcing the blood to enter the aorta and to continue around the systemic circulation
- 6. Coronary Artery Anatomy • There are two main coronary arteries. • Left main coronary artery –Subdivides into left anterior descending artery and circumflex artery • Right coronary artery • These sub divide into smaller branches.
- 7. Aorta Right Coronary Artery Left Main Coronary Artery Left Circumflex Branch Left Anterior Descending Marginal Branch Posterior descending artery Anterior heart showing coronary vessels
- 8. Coronary Veins • Coronary veins run alongside the coronary arteries and return deoxygenated blood from the myocardium to the right atrium through the coronary sinus
- 9. Limb Leads Right Arm Right Leg Left Leg Left Arm • Limb leads are typically placed on the inside of the wrists and ankles • To help reduce artifacts you can use the upper arms and thighs • Do not place limb leads on the torso
- 11. V1 V1 V2 V2 V3 V3 V4 V4 V5 V5 Horizontal plane - the six chest leads V6 V6 RA LA LV RV
- 12. Normal 12 Lead ECG
- 13. ECG: Wave pattern atrial systole ventricular systole atrial/ventricular diastole OMillivolts P T R S Q Complete cardiac diastole 0.4s Ventricular systole 0.3s Atrial systole 0.1s
- 17. Spread of electrical activity through the atria P
- 18. Atrioventricular node and the bundle of His
- 19. The heart in action P R Q S T
- 20. ST Segment
- 21. Pathological Q Wave > 0.04 sec wide >25% of R wave
- 22. ST Segment 1 2 3
- 23. • Stable Angina • Acute coronary syndromes – Unstable angina • Pain +/- ECG changes but NORMAL enzymes – NSTEMI (non ST-elevation myocardial infarct) • Pain +/- ECG changes AND raised Troponin – STEMI (ST-elevation myocardial infarct) • Pain with ST elevation on ECG AND raised Troponin Coronary Syndromes White thrombus Red thrombus
- 24. Stable Angina
- 26. Unstable angina and NSTEMI
- 30. Treatment • Antiplatelets – Aspirin and Clopidogrel • Anticoagulants – Low molecular weight heparin • Beta-blocker, Statin, ACE inhibitor • Standby coronary angiogram
- 34. Acute ST elevation Myocardial Infarction 15 minutes 2 hours 6 hours % necrosis 0% 50% 90%
- 35. Treatment • Aspirin • Thrombolysis • Beta-blocker, Statin, ACE inhibitor • Exercise test – if positive, standby coronary angiogram In the not too distant future: • Primary PCI (angioplasty and stent)
Editor's Notes
- This slide illustrates the main structures of the heart. The heart is separated into 4 chambers, namely the left and right atria and the left and right ventricles. A septum separates the heart into the left and right side. The chordae tendinae and papillary muscles keep the flaps of the valves pointing in the direction of the blood flow as it passes through the atria and ventricles. The heart actually functions as two separate pumps – on the right hand side, the heart pumps blood to the lungs; on the left-hand side, the heart pumps blood throughout the rest of the body. The muscle wall of the left ventricle is 3 to 4 times thicker than the right. This is due to the amount of work required to pump blood through the aortic valve into the aorta, which then branches to supply the rest of the body with oxygenated blood.
- As per the slide
- The heart wall has its own circulatory system which consists of the left and right coronary arteries that originate from the base of the aorta. Where branches from different arteries supply the same region, they often join up, or connect with one another. This is referred to as anastomosis. Anastomoses provide what is known as “ collateral circulation” which provides alternative routes for blood to reach the heart in the event of an occlusion. Although most collaterals in the heart are quite small, heart muscle can remain alive as long as it receives as little as 10 – 15% of its normal supply.
- As per the slide
- While there are 4 limb electrodes / cables, it is important to remember that the electrode attached to the right leg plays no part in the formation of any lead – it is only there to stabilise the ECG. Although the fronts of the wrists and ankles are common positions for the attachment of cables to electrodes, all parts of the limb will give an identical electrical signal. However, it is NOT good practice to place limb electrodes on either the abdomen or shoulders.
- Impulse transmission through the conduction system generates electrical currents that can be detected on the surface of the body. A recording of this electrical activity that accompanies the cardiac cycle is called and electrocardiogram (ECG). In a normal ECG recording, 3 recognisable waves accompany each cardiac cycle (heartbeat). The first, known as the P wave is a small positive wave, which indicates the spread of an impulse from the SA node through the muscle of the 2 atria. The second, known as the QRS wave (complex) begins as a negative deflection, continues as a large positive wave and ends as a negative wave. This represents the spread of the electrical impulse through the ventricles. The third deflection is a dome-shaped T wave. This indicates ventricular repolarisation. There is no deflection to show atrial repolarisation as the QRS complex masks this event. If we assume that the average heart rate is 75 bpm, then each cardiac cycle requires approximately 0.8 seconds. During the first 0.1 sec, the atria contract and the ventricles relax. For the next 0.3 sec, the atria are relaxing and the ventricles are contracting. The last 0.4-sec of the cycle is relaxation period, and all chambers are in diastole.
- The ST segment denotes the time from end of ventricular contraction to the beginning of the resting phase. ST segment should not deviate from the isoelectric line in the normal ECG except in lead V1 & V2 where there may be minimal elevation (normal variant).
- Pathological Q waves are 0.04 seconds (one small square) or longer in width and as a guide, their depth is approximately >25% of the height of the ensuing R wave. Q waves are usually associated with a substantial loss in amplitude (height) of the ensuing R wave. Pathological Q waves are usually grouped in several leads associated with the site being viewed i.e. inferior or lateral. Q waves are a late sign of full thickness myocardial infarction and are non-reversible.
- The ST segment is measured in small squares / millimetres (mm). 1. Demonstrates a normal ST segment 2. ST depression, below the isoelectric line. 3. ST elevation above the isoelectric line.
- Necrosis progresses from the subendocardium to the pericardium. As a consequence of ischaemia, necrosis (cell death) occurs first in the subendocardium beginning as early as 15 to 20 minutes after coronary artery occlusion. With longer occlusions, a wavefront of cell death moves from the subendocardial zone (inner layer) to involve progressively more of the transmural thickness (outer layer) of the myocardium. The recognition of the time-dependent progression of necrosis is the basis of interventions designed to arrest the progression of necrosis as rapidly as possible by reperfusion of occluded coronary arteries, using thrombolytic therapy.