Lesson Four

COMMON NONINVASIVE DIAGNOSTIC TESTS

CHAPTER 24

The ECG Paper

Horizontally One small box - 0.04 s One large box - 0.20 s

Vertically One large box - 0.5 mV

The ECG Paper (cont)

Every 3 seconds (15 large boxes) is marked by a vertical line.

This helps when calculating the heart rate.

3 sec 3 sec

The 12-Leads

The 12-leads include:

–3 Limb leads (I, II, III)

–3 Augmented leads (aVR, aVL,

aVF)–6 Precordial leads

(V1- V6)

Views of the Heart

Some leads get a good view of the:

Anterior portion of the heart

Lateral portion of the heart

Inferior portion of the heart

ST Elevation

One way to diagnose an acute MI is to look for elevation of the ST segment.

Anterior View of the Heart

The anterior portion of the heart is best viewed using leads V1- V4.

Rate Rhythm Axis Intervals Hypertrophy Infarct

Right atrial enlargement Take a look at this ECG. What do you notice about the P waves?

The P waves are tall, especially in leads II, III and avF. Ouch! They would hurt to sit on!!

SUMMARY Rate Rhythm Axis Intervals Hypertrophy Infarct

Infarct: Are there T wave changes?

No

Rhythm Summary

Rate 90-95 bpm Regularity regular P waves normal PR interval 0.12 s QRS duration 0.08 sInterpretation?

Normal Sinus Rhythm

Rhythm #1

30 bpm• Rate?• Regularity? regular

normal

0.10 s

• P waves?

• PR interval? 0.12 s• QRS duration?

Interpretation? Sinus Bradycardia

Rhythm #2

130 bpm• Rate?• Regularity? regular

normal

0.08 s

• P waves?

• PR interval? 0.16 s• QRS duration?

Interpretation? Sinus Tachycardia

Rhythm #3

70 bpm• Rate?• Regularity? occasionally irreg.

2/7 different contour

0.08 s

• P waves?

• PR interval? 0.14 s (except 2/7)• QRS duration?

Interpretation? NSR with Premature Atrial Contractions

PVCs

Deviation from NSR Ectopic beats originate in the ventricles

resulting in wide and bizarre QRS complexes.

When there are more than 1 premature beats and look alike, they are called “uniform”. When they look different, they are called “multiform”.

1st Degree AV Block

Deviation from NSRPR Interval > 0.20 s

2nd Degree AV Block, Type I

Deviation from NSRPR interval progressively lengthens,

then the impulse is completely blocked (P wave not followed by QRS).

3rd Degree AV Block

Deviation from NSRThe P waves are completely blocked

in the AV junction; QRS complexes originate independently from below the junction.

ELECTROCARDIOGRAPHY

The ECG / EKG. The tracing given by the evaluation

of electrical impulses generated by the heart during depolarization (contraction) and repolarization (relaxation).

ELECTROCARDIOGRAPHY

USED IN THE EVALUATION OF

CHEST PAIN - ISCHEMIA VS. INFARCTION. RHYTHM DISTURBANCES / ARRHYTHMIAS. DRUG TOXICITY – digitalis, quinidine. METABOLIC EFFECTS – electrolytes, hyper

and hypokalemia, calcium, magnesium. CONDUCTION DEFECTS – heart block(s).

HOLTER MONITOR

An ambulatory electrocardiograph. Used to detect / evaluate arrhythmias

that are episodic. Also used to assess response to

treatment.

ELECTROENCEPHALOGRAPHY The EEG. Records electrical activity of the brain, mainly the

superficial layers of the cortex. Used to detect foci of abnormal activity, such as in

epilepsy. ALSO: brain death, sleep studies (the “somnogram”),

sleep apnea, narcolepsy, etc

ELECTROMYELOGRAPHY

THE EMG – measures electrical activity of muscle.

Used to evaluate neuromuscular disorders, to differentiate between neuropathy (primary disease of motor neurons, such as polio), and myopathy (primary disease of muscle, such as myesthenia gravis).

Normal recruitment pattern . (A) With minimal effort: a single

motor unit is seen firing at 6 Hz. The time between 2 discharges is approximately 166 milliseconds (ms),

(B) Gradual increase in muscle strength results in recruitment of a second motor unit. In this example, it is 12 Hz, the reciprocal of the recruitment interval, which is 85 ms.

(C) With further increase in muscle strength, a third motor

unit is recruited.

Amyotphic Lateral Sclerosis: rapid firing unit

myositis, many motor units are activated simultaneously at a low level of muscle contraction. Note the low amplitude and short duration of individual units.

45-year-old man presented with a 6-month history of progressive muscle weakness. Atrophy of several leg muscles and intrinsic hand muscles accompanied by occasional fasciculations but no sensory loss. The recording is from the anterior tibial muscle.

The motor unit firing at about 25 Hz indicates decreased recruitment as in a neurogenic disorder. The most likely cause in this setting of widespread motor involvement without sensory findings is a motor neuron disorder or motor

neuropathy.

PULMONARY FUNCTION TESTS

The PFT’s. Assessment of inspiration and expiration to

determine if a respiratory problem is due to an obstructive defect, a restrictive defect, or both.

OBSTRUCTIVE- an increase in airway resistance; Ex: asthma, COPD.

RESTRICTIVE- a limitation of chest expansion; Ex: pulmonary fibrosis, muscular dystrophy, obesity, severe scoliosis.

PULMONARY FUNCTION TESTS See text re the various parameters, the

FVC, the FEV-1, etc.

The Alveolar Sac

PEAK FLOW TESTING

A hand-held gizmo used in ambulatory monitoring of air flow in patients w/ asthma.

Monitors expiratory capacity, and can be plotted on a daily basis to assess for decreased flow.

Is a sensitive monitor of increased resistance, and can show a change before a patient becomes symptomatic.

Can thus be used for intervention prior to a full-blown flare-up.

http://www.mayoclinic.com/health/asthma/MM00399

Peak Expiratory Flow (liters per minute) 

Age (Years)

HEIGHT   Age (Years)

HEIGHT

60” 65” 70” 75” 80” 55” 60” 65” 79” 75”

20 554 602 649 693 740 20 390 423 460 496 529

25 543 590 636 679 725 25 385 418 454 490 523

30 532 577 622 664 710 30 380 413 448 483 516

35 521 565 609 651 695 35 375 408 442 476 509

40 509 552 596 636 680 40 370 402 436 470 502

45 498 540 583 622 665 45 365 397 430 464 495

50 486 527 569 607 649 50 360 391 424 457 488

55 475 515 556 593 634 55 355 386 418 451 482

60 463 502 542 578 618 60 350 380 412 445 475

65 452 490 529 564 603 65 345 375 406 439 468

70 440 477 515 550 587 70 340 369 400 432 461

Peak Expiratory Flow RateNORMAL CHILDREN AND ADOLESCENTS

HEIGHT (INCHES)

MALES & FEMALES

HEIGHT (INCHES)

MALES & FEMALES

HEIGHT (INCHES)

MALES & FEMALES

43 147 51 254 59 360

44 160 52 267 60 373

45 173 53 280 61 387

46 187 54 293 62 400

47 200 55 307 63 413

48 214 56 320 64 427

49 227 57 334 65 440

50 240 58 347 66 454

UREA BREATH TEST FOR H. pylori

H. pylori the cause of many cases of gastritis and peptic ulcer.

If detected, can be eradicated and disease healed.

H. pylori produces an urease, an enzyme that breaks down urea, creating CO2 that is absorbed from the GI tract then exhaled.

Test measures changes in CO2 from baseline to after patient is given synthetic urea.

Serologic (antibody) tests exist, but can not differentiate between current and prior infection.

CHAPTER 26

STRESS TESTS. CARDIAC CATH. ELECTROPHYSIOLOGIC STUDIES. SYNCOPE TESTS.

STRESS TESTS

See http://www.emedicine.com/med/topic2961.htm

For an excellent, comprehensive review of exercise stress testing.,

STRESS TESTS

A test in which a patient exercises on a treadmill, thereby increasing cardiac demand for oxygen while oxygen consumption in skeletal muscle increases.

EKG monitoring is done, looking for evidence of ischemia, ie ST segment depression.

STRESS TESTS

USED FOR 1) Assessment of probability of and extent

of coronary artery disease (CAD). 2) Estimate prognosis in patients w/ CAD. 3) Determine functional capacity. 4) Assess the effects of therapy. 5) Assess need for cardiac cath and / or

coronary revascularization.

STRESS TESTS Mortality – your text says 1 death per

10,000 procedures; eMedicine web site says 1 per 2500. Either way, not a 100% benign study.

Sometimes used in conjuction w/ thallium radionuclide study, whereby post-exercise scans are used to assess myocardial perfusion. The “Thallium Stress Test” or “Thallium Treadmill.”

CARDIAC CATHETERIZATION

Catheterization of the left side of the heart via the femoral artery, or the right side of the heart via the IVC. Dye is injected to assess anatomy of the heart and patency of the coronary arteries.

If aortic stenosis is present the left heart can be assessed from the right heart via the “trans-septal” technique in which a needle injects the dye thru the interventricular septum.

Measurements are taken of pressure to assess flow, and O2 to assess oxygenation.

CARDIAC CATHETERIZATION

USES Assess cardiac malformations – congenital

and acquired such as valvular defects. Assess need for coronary

revascularization, which can be done at the same time via balloon angioplasty, or later via CABG.

OCCLUSION OF THE L.A.D.

ELECTROPHYSIOLOGIC STUDIES

A type of cardiac cath in which electrodes are used to assess cardiac conduction.

Can locate the focus of aberrant conduction pathways.

Can be used for diagnostic as well as therapeutic purposes, such as treatment of tachyarrhythmias.