Wigger\'s Diagram pdf - Lecture notes 5 PDF

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Wigger’s Diagram: -

Correlates the events that occur concurrently during the cardiac cycle o ECG features, Pressure/Vol changes, valve activity, heart sounds Only events on LHS are described – same on RHS but pressures are lower 1 full cycle begins + ends with ventricle diastole

1. Atria + Ventricle in diastole • TP segment in ECG : displays the interval after ventricle repolarization • Passive filling – ventricular volume continues to rise slightly before atrial contraction takes place • The continuous inflow of the venous system, which enter the atria, cause atrial pressure to slightly exceed ventricular pressure during diastole 2. Atrial systole - depolarisation • Due to SA node reaching threshold + firing – shown by the P wave in ECG • Atrial contraction: atrial pressure rises (slightly higher than ventricular pressure, meaning the Mitral valve is still open) • Ventricular volume increase - more blood squeezed into ventricle • Excitation-Contraction-Coupling takes place during short delays between P wave and rise in atrial pressure 3. End of ventricular diastole (diastole = isovolumetric relaxation + ventricular filling) • Atrial contraction + ventricular filling is complete • EDV = 135ml (vol of blood in ventricle at end of diastole) 4. Onset of Ventricular systole (systole = isovolumetric contraction + ventricular ejection) • Impulse goes to AV node and down specialised conduction system • excites ventricle – forms QRS complex • Atria contract simultaneously • As ventricular contraction begins, ventricular pressure exceeds atrial pressure and Mitral valve closes 5. Isovolumetric contraction • To open aortic valve, ventricular pressure must exceed aortic pressure • Aortic valve opens • Ventricle remains briefly closed- no blood enters or leaves the ventricle • Chamber stays at constant volume, muscle fibres at constant length whilst the ventricular pressure is still rising 6. Ventricular Ejection • Aortic valve open + blood ejects • SV = amount of blood pumped out of each ventricle with each contraction • Aortic pressure rises as blood forced into aorta • Ventricular volume decreases 7. End of Ventricular systole • Ventricle doesn’t empty completely • ESV = amount of blood left in ventricle at the end of systole when ejection is complete (approx. 65ml) 8. Aortic valve closes • Mitral valve still closed

Aortic valves close which creates a disturbance in the aortic curve called Dicrotic notch! • Brief period that all valves are closed = isovolumetric ventricle relaxation • Ventricle relaxes, pressure falls 9. Ventricular filling • Ventricle pressure falls below atrial pressure: TP segment • Mitral valve opens •

When body is at rest, one complete cardiac cycle lasts 800 msec - 300msec : ventricular systole - 500msec : ventricular diastole When heart rate increases (as a result of stress/exercise) - Diastole length shortened - Less ventricle filling...