Question

A. Data and Calculations Subject Profile Name Gender Age Height- Weight 1. Record your data in Table 37.4 Table 37.4 Measurement of R-R Interval for Cardiac Cycle Duration Cardiac Cycle Cycle 2 Condition Cycle 1 Cycle 3 Mean Segment 1: Supine Value [CH 40 BPM (CH 11 Value [CH 40] Segment 2: Seated -- Segment 3: Start of Inhale Value [CH 40] Value [CH 40] BPM (CH 1] Value [CH 40] BPM ICH 11 Segment 3: Start of Exhale - Segment 4: After Exercise - 2. Record your data in Table 37.5. Table 37.5 Duration of Ventricular Systole and Ventricular Diastole Delta T (CH 1 Ventricular Systole Ventricular Diastole Segment 1: Supine Segment 4: After Exercise 3. Record your data in Table 37.6 Table 37.6 ECG Duration and Amplitude Duration Delta T ICH1) of Segment 1 Cycle Amplitude (mV) P-P [CH 1] of Segment 1 Cycle Normative Values Seg 1 3 Mean (calo) ECG Based on Resting Heart Seg 1 3 Mean (cale.) Rate of 75 BPM Duration (sec) Amplitude (mV 4 20 10-1.5 Waves P wave 07-.18 Q-R-S complex .06-.12 T wave 10-,25 Intervals P-R Q-T Duration (sea) 12-20 32-36 .80 Duration (sec) 02-.10 R-R Segments P-R S-T T-P

Answer 1

1.  Under these conditions, there is NO PR interval (since the P wave didn't cause theQRS complex). The atria and the ventricles are functioning entirely independently of each other. However, both P waves and QRS complexes are still identifiable on the ECG.

2.  P Wave:

The P wave represents depolarization of the right and left atria.

Onset of the P Wave is identified as: the first abrupt or gradual deviation from the baseline. The point where the wave returns to the baseline marks the end of the P Wave. A QRS complex normally follows each P Wave. A normal sinus P Wave indicates that the electrical impulse responsible for the P Wave originated in the SA node and that normal depolarization of the right and left atria has occurred

A T Wave represents ventricular repolarization.

Repolarization of the ventricles begins at the epicardial surface of the ventricles and progresses inwardly through the ventricular walls to the endocardial surface. The T Wave occurs during the last part of the ventricular systole. The onset of the T Wave is the first or abrupt or gradual deviation from the S-T segment; or from the point where the slope of the S-T segment appears to become abruptly of gradually steeper. If the S-T segment is absent, the T Wave begins at the end of the QRS Complete (or the J Point). The point where the T Wave returns to the baseline marks the end of the T Wave. Often the onset and end of the T Wave are difficult to determine with certainty.

1. The DURATION of the T Wave is 0.10 to 0.25 seconds or greater.
2. The AMPLITUDE of the T Wave is less than 5 mm.
3. The SHAPE of the T Wave is sharply or bluntly rounded and slightly asymmetrical.
4. A T Wave always follows a QRS Complex.

P WAVE

SA atria atria AV AV ventricles

T WAVE

ST segment

4.  CHANGES IN THE ELECTROCARDIOGRAM (ECG) during exercise in normal subjects were described by Simonson in 1953.' He observed decreased R wave amplitude and right axis deviation as well as junctional depression of the ST segment and decreased T wave amplitude. Sjostrand2 showed that the depression of the QRS-ST junction during exercise in normal subjects is related to heart rate. Later, Irisawa3 demonstrated a marked increase of the P wave amplitude during exercise. These findings have been confirmed in recent years by quantitative ECG analysis with modern computer techniques. 4-12 Blomqvist4 " and Bruce et al.5' 6 demonstrated that such ECG changes occur gradually when a multistage exercise test is performed. In the recovery period, these changes reverse, although the relation between ST-segment amplitude and heart rate in the recovery period seems to follow a different pattern than during exercise.' `

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