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Cardiac Cycle The two atria contract at the same time, then they relax while the two ventricles simultaneously contract. The two atria contract at the.

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Presentation on theme: "Cardiac Cycle The two atria contract at the same time, then they relax while the two ventricles simultaneously contract. The two atria contract at the."— Presentation transcript:

1 Cardiac Cycle The two atria contract at the same time, then they relax while the two ventricles simultaneously contract. The two atria contract at the same time, then they relax while the two ventricles simultaneously contract. The contraction phase of the ventricle chambers is called systole. The contraction phase of the ventricle chambers is called systole. The relaxation phase is called diastole. The relaxation phase is called diastole. At a normal heart rate, one cardiac cycle last for 0.8 seconds! At a normal heart rate, one cardiac cycle last for 0.8 seconds!

2 Cardiac Cycle Continued…. Cardiac Cycle = events of one complete heart beat Cardiac Cycle = events of one complete heart beat Mid-to-late diastole (relaxation) = blood flows into ventricles Mid-to-late diastole (relaxation) = blood flows into ventricles Ventricular systole (contraction) = blood pressure builds before ventricles contract pushing blood out Ventricular systole (contraction) = blood pressure builds before ventricles contract pushing blood out Early diastole = atria finish re-filling; ventricular pressure is low Early diastole = atria finish re-filling; ventricular pressure is low

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4 The Normal Conduction System

5 The electrocardiogram (EKG or ECG) is a graphic display of the electrical events of the cardiac cycle. What is an Electrocardiogram? Each event has a distinctive waveform, the study of which can lead to greater insight into a patients cardiac output.

6 EKG Waves

7 Wave Interpretation P Wave = contraction of atria P Wave = contraction of atria PQ Wave = signal arrives at AV node slowing down a bit to allow ventricles to fill with blood PQ Wave = signal arrives at AV node slowing down a bit to allow ventricles to fill with blood Q Wave = signal moves to Bundle of His and divides into the bundles and Purkinje fibers Q Wave = signal moves to Bundle of His and divides into the bundles and Purkinje fibers R Wave = contraction of left ventricle R Wave = contraction of left ventricle S Wave = contraction of right ventricle S Wave = contraction of right ventricle T Wave = ventricles relaxing T Wave = ventricles relaxing

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9 Rule of 300 Take the number of big boxes between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the heart rate Take the number of big boxes between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the heart rate Although fast, this method only works for regular rhythms. Although fast, this method only works for regular rhythms.

10 What is the heart rate? (300 / 6) = 50 bpm

11 What is the heart rate? (300 / ~ 4) = ~ 75 bpm

12 What is the heart rate? (300 / 1.5) = 200 bpm

13 10 Second Rule As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds. As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds. This method works well for irregular rhythms. This method works well for irregular rhythms.

14 What is the heart rate? 33 x 6 = 198 bpm

15 Pulse Heart Rate Pulse Pulse Pressure wave of blood Pressure wave of blood Monitored at pressure points in arteries where pulse is easily palpated Monitored at pressure points in arteries where pulse is easily palpated Pulse averages 70–76 beats per minute at rest Pulse averages 70–76 beats per minute at rest

16 Blood Pressure Measurements by health professionals are made on the pressure in large arteries Measurements by health professionals are made on the pressure in large arteries Systolicpressure at the peak of ventricular contraction Systolicpressure at the peak of ventricular contraction Diastolicpressure when ventricles relax Diastolicpressure when ventricles relax Write systolic pressure first and diastolic last (120/80 mm Hg) Write systolic pressure first and diastolic last (120/80 mm Hg) Pressure in blood vessels decreases as distance from the heart increases Pressure in blood vessels decreases as distance from the heart increases

17 Measuring Arterial Blood Pressure

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