### The ECG (continued...)

#### Analysis: (continued..)

ECG's are analyzed on the basis of a number of characteristics:
sequence of waves (Table 16)
heart rate
duration of waves and intervals
amplitude and shape (Table 17)
rhythm
electrical axis (Table 18)

Heart rate (Table 16) can be determined in one of three ways:

• by dividing 60 (sec/min) by the R-R interval (in sec). (Table 19)

• by observing the distance between two adjacent R waves (or any wave) and if they lie 1 large division apart calling the rate 300 per min. (if they are 2 large divisions apart the rate is 150 per min, 3 apart 100, 4 apart 76, 5 apart 60, etc.) (Table 20). Figure 8 shows strips from two people, one an athlete and the other sedentary. Determine heart rate by the three methods described.

• by counting the number of R waves per 6 sec interval and multiplying by 10. (Table 21)

At the standard paper speed of 25 mm/sec., the heavy vertical lines are 200 msec apart and the fine vertical lines are 40 msec apart. Most paper also has 6 sec. markers along either edge. The second method is faster but less accurate.

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