i bc27f85be50b71b1 (12 page)

recorded on a tape, and the subsequent analysis follows from this

recording.

Indications for Holter monitoring include the evaluation of syncope, dizziness, shortness of breath with no other obvious cause, pal-

26 AClffE CARE HANDBOOK FOR PHYSICAL THERAPISTS

Table 1 -10. Electrocardiograph Interpretation

Duration

Wave/Segment

(sees)

Amplitude (mm)

Indicates

P wave

<0. 10

1-3

Atrial depolarization

PR interval

0.12-1).20

Isoelectric line

Elapsed time between atrial

depolarization and ven·

tricular depolarization

QRS complex 0.06-1).10 25-30

Ventricular depolarization

(maximum)

and atrial repoiariz3tion

ST segment

0.12

-1/2 co +1

Elapsed time between the

end of ventricular depo·

larization and the beginning of repolarization

QT interval

0.42-1).47

Varies

Elapsed time between the

(QTc)

beginning of ventricular

repoiarization and the

end of repolarization

(QT c is corrected for

heart rate)

T wave

0.16

5-10 mm

Ventricular repolariz3rion

Sources: Data from RS Meyers (ed). Saunders Manual of Physical Therapy Practice.

Philadelphia: Saunders, 1 995; B Aehlen (ed). ACLS Quick Review Study Guide. St.

Louis: Mosby, 1 994; and D Davis (ed). How to Quickly and Accurately Mast'er ECG

Interpretation (2nd ed). Philadelphia: Lippincott, 1992.

pitations, antiarrhythmia therapy, pacemaker functioning, actlvltyinduced silent ischemia, and risk of cardiac complications with the use of heart rate variability (HRV).

Heart Rate Variability

The most common measure of HRV is the standard deviation of all

HR intervals during a 24-hour period (SONN).8 HRV has been used

in clinical studies to test a variety of health outcomes.8•14-16 In

healthy populations, low HRV has been shown to be a risk factor

for all causes of cardiac mortality,'7-19 as well as new onset of

hypertension.2o Low HRV is also a risk for mortality in patients

who have had an MI,21-23 have coronary artery disease,24 or have

CHF.25 A classic study performed by Kleiger et al.26 demonstrated a

fivefold risk of re-infarction in post-MI patients with an SON (in

CARDIAC SYSTEM

27

milliseconds) of less than 50, when compared to patients with an

SDNN of greater than 100.

Telemetric Electrocardiogram Monitoring

Telemetric ECG moniroring provides real time ECG visualization via

radiofrequency transmission of the ECG signal ro a moniror. Telemetry has the benefit of Holter monitoring (because there is no hard wire connection of the patient to the visual display unit) as well as the benefit of the standard ECG monitor attachment, because there is a realtime graphic display of the ECG signal.

Clinical Tip

• Some hospitals use an activity log with Holter monitoring. If 0, be sure to document physical therapy intervention on the log. If there is no log, be sure to document time of day and intervention during physical therapy in the

medical record.

• The use of cellular phones, although usually prohibited

in any hospital, is especially prohibired on a telemetry

unit. The cellular phone may interfere with the radio frequency transmission of the signal.

Complete Blood Cell Count

Relevant values from the complete blood cell count are hematocrit,

hemoglobin, and white blood cell counts. Hematocrit refers to the

number of red blood cells per 1 00 ml of blood and therefore Auctuates with changes not only in the total red blood cell count (hemoglobin) but also with blood volume. Elevated levels of hematocrit (which may be related to dehydration) indicate increased viscosity of blood that can potentially impede blood Aow to tissues. 12

Hemoglobin is essential for the adequate oxygen-carrying capacity

of the blood. A decrease in hemoglobin and hematocrit levels

( 1 0% below normal is called anemia) may decrease activity tolerance or make patients more susceptible to ischemia secondary to decreased oxygen-carrying capacity. "·27 Slight decreases in hematocrit due to adaptations to exercise (with no change in hemoglobin) are related to increases in blood volume. The concomitant exercise-related decreases in blood viscosity may be beneficial to

post-MI patients.28

28 AClJrE CARE HANDBOOK FOR PHYSICAL THERAPISTS

Elevated white blood cell Counts can indicate that the body is fighting infection, or they can occur with inflammation caused by cell death, such as in MI. Erythocyte sedimentation rate (ESR), another

hematologic test, is a nonspecific index of inflammation and is commonly elevated for 2-3 weeks after MIP Refer to Chapter 6 for more information about these values.

Coagulation Profiles

Coagulation profiles provide information about the c10rting time of

blood. Patients who undergo treatment with thrombolytic therapy

after the initial stages of MI or who are receiving anticoagulant therapy owing to various cardiac arrhythmias require coagulation profiles ro moniror anticoagulation in an attempt to prevent complications,

such as bleeding. The physician determines the patient's therapeutic

range of anticoagulation by using the prothrombin time (PT), partial

thromboplastin time, and international normalized ratio.17 Refer ro

Chapter 6 for details regarding these values and their significance to

treatment.

Patients with low PT and partial thromboplastin time are at higher

risk of thrombosis, especially if they have arrhythmias (e.g., atrial

fibrillation) or valvular conditions (mitral regurgitation) that produce