tests associated with cardiac disorders

TESTS ASSOCIATED

WITH CARDIAC DISORDERS

Cardiac disorders :

primary diagnosis :Auscultation.

Detecting abnormal heart sounds.

Blood pressure – sphygmomanometer.

SIGNS AND SYMPTOMS:

Chest pain.

Dyspnea with or without orthopnea.

Paroxysmal nocturnal dyspnea.

Cyanosis.

Fatigue.

Palpitations.

Cough.

Edema.

Syncope.

Abnormal heart sounds.

DIAGNOSIS OF CARDIAC DISORDERS:

Heart sounds

Laboratory tests

Chest X-ray

Electrocardiogram

Ambulatory ECG Monitoring

Echocardiogram

Doppler echocardiography

Transoesophageal echocardiography

Cardiac catheterisation

Angiography

Computed tomography

Magnetic resonance imaging

Radiology

Radionuclide imaging

HEART SOUNDS: Stethoscope is the commonest instrument used. FIRST SOUND: (L-U-B-B) Occurs at the onset of ventricular systole.o DURATION: 0.1 – 0.17 seco CAUSES: Occurs due to sudden closure of the AV valves. Ejection of blood from the ventricles & the vibration transmitted to the walls of the pulmonary artery & aorta.

o SIGNIFICANCE: Indicate the condition of myocardium. Indicates proper closing of AV valves.o CLINICAL IMPLICATIONS: INCREASED FIRST SOUND: Hypertrophy. SHORT & LOW PITCHED FIRST SOUND: Myocardial weakness.

SECOND SOUND: (DUP)

Occurs at the onset of the diastole.

o DURATION: 0.1 -0.14 sec

o CAUSES:

Caused by the sudden closure of the semi lunar valves in the aorta & pulmonary artery.

o SIGNIFICANCE:

Indicates the end of systole & beginning of diastole.

Its pitch is directly proportional to the BP.

Indicates proper closing of semilunar valves.

o CLINICAL IMPLICATIONS:

DECREASED DIASTOLIC PERIOD: ( PAUSE)

Increased heart rate.

THIRD SOUND:

o DURATION: 0.04 sec

o CAUSES:

Sudden rush of atrial blood.

o SIGNIFICANCE:

Indicates ventricular filling.

FOURTH SOUND:

o DURATION: 0.01 sec

o CAUSE:

Contraction of atria

o SIGNIFICANCE:

Indicates the ending of ventricular filling.

LABORATORY TESTING :

1. BLOOD TESTS :

SERUM CHOLESTROL :

o Total cholesterol : 150 – 200 mgs

o TGL : Up to 170 mgs

o HDL : 35 – 55 mgs

o LDL : Up to 170 mgs

o VLDL : 20 – 40 mgs

CLINICAL IMPLICATION :

• Elevated cholesterol level (HYPERCHOLESTEROLEMIA )

Coronary heart disease

Hypothyroidism

Diabetes mellitus

Cholestasis

Hepatocellular disease

Biliary cirrhosis

Glomerulonephritis

Werner’s syndrome

Obesity

Chronic renal failure

• Decreased cholesterol level: ( HYPOCHOLESTEROLEMIA )

Myleoproleferative diseases

Hyperthyroidism

Malnutrition

Megaloblastic anemia

Severe burns

Inflammation

Infection

Chronic obstructive lung disease

Mental retardation

HIGH DENSITY LIPOPROTEIN CHOLESTEROL :

Normal value : 35 -55 mgs

CLINICAL IMPLICATIONS :

o ↓ HDL-C Values:

Uremia

Hepatocellular disease

Chronic renal failure

Cholestasis

Diabetes mellitus

o ↑ HDL-C Values:

Atherosclerosis

Myocardial occlusion

LOW DENSITY LIPOPROTEIN (LDL)

Normal value : Up to 170 mgs

CLINICAL IMPLICATIONS :

o Increased LDL levels:

Premature CHD

Hyperlipidemia

Nephrotic syndrome

Chronic renal failure

Porphyria

Myocardial infarction

Coronary artery occlusion

Anorexia nervosa

oDecreased LDL levels :

Hypoproteinemia

Tangier disease

Hyperthyroidism

Chronic anemias

Severe hepatocellular disease

Reye’s syndrome

Acute stress

Inflammatory joint disease

Chronic pulmonary disease

2. ENZYME TESTS :

ENZYME NORMAL LEVEL

DISEASE CONDITION

SGOT Up to 40 U/LT Myocardial Infarction

LDH M→82-285 U/LTW→103-227 U/LT

Congestive cardiac failure

CPK M→<190 U/LTW→>165 U/LT

Various heart disease

AST / SGOT : NORMAL VALUES:

MEN : 14 – 20 U/L

WOMEN : 10-36 U/L

CLINICAL IMPLICATIONS:

Increased AST levels occur in MI:

Increased to 4-10 times the normal value.

AST level reaches a peak in 24 hrs & returns to normal by post MI day 3-7.

Secondary rise in AST levels suggest extension or recurrence of MI.

Increased AST levels occur in liver diseases:(10-100 times normal)

Acute hepatitis & chronic hepatitis ( ALT > AST)

Active cirrhosis( drug induced ; alcohol induced :( AST >ALT)

Hepatic necrosis & metastasis

Primary or metastatic carcinoma

Alcoholic hepatitis

Reye’s syndrome

Other diseases with elevated AST levels:

Hypothyroidism

Trauma & irradiation of skeletal muscle

Shock

Hemolytic anemia

Decreased AST levels:

Azotemia

Chronic renal dialysis

Vitamin B6 deficiency

LDH ( LACTATE DEHYDROGENASE) NORMAL VALUES:

MEN : 82-285 U/L

WOMEN : 103-227 U/L

CLINICAL IMPLICATIONS:

Increased LDH levels:

High levels occur within 36-55 hrs after MI & continue longer than elevations of SGOT or CPK ( 3-10 days)

In pulmonary infarction increased LDH occurs within 24 hrs of pain onset . The pattern of normal SGOT & elevated LDH levels of 1-2 days after an episode of chest pain – pulmonary infarction.

Congestive heart failure

Liver diseases ( cirrhosis, alcoholism, acute viral hepatitis )

Cancer , leukemia

Hypothyroidism

Lung diseases

Skeletal muscle diseases

Megaloblastic & pernicious anemias , hemolytic anemia, sickle cell disease

Seizures

Shock, hypotension

Renal infarction

LACTATE DEHYDROGENASE ISOENZYMES :

NORMAL VALUES :

LD1 : 17-27% of total or 0.17-0.27

LD2 : 29-39% of total or 0.29-0.39

LD3 : 19-27% of total or 0.19-0.27

LD4 : 8-16% of total or 0.08-0.16

LD5 : 6-16% of total or 0.06-0.16

CLINICAL IMPLICATIONS:

DISEASE LD1 LD2 LD3 LD4 LD5

Myocardial infarction

√ √

Pulmonary infarction

√ √

Congestive heart failure

√ √

Viral hepatitis

√ √

Toxic hepatitis

√ √

DISEASE LD1 LD2 LD3 LD4 LD5

Leukemia √ √

Pancreatitis

√ √

Carcinomatosis (extensive)

√ √

Megaloblastic anemia

√ √

Hemolytic anemia

√ √

Muscular dystrophy

√ √

CHEST X-RAY:

First diagnostic test in cardiac work shop.

Provides global information about position & size of the heart & chambers & surrounding anatomy.

The std CXRs for evaluation of lungs & heart are standing posteroanterior & lateral views taken at maximal inspiration.

Portable CXRs – less satisfactory.

The PA CXR outlines superior vena cava , right atrium on the right & left sides , aortic knob ,main pulmonary artery, left atrial appendage & left ventricle.

In the lateral view CXR visualizes right ventricle , inferior vena cava & left ventricle.

Cardiac enlargement is determined by cardio thoracic ratio.

ELECTROCARDIOGRAM ( ECG ) :

Painless process.Records the electrical

activity of the heart.Detected from the body

surface by electrodes ( leads ) and a galvanometer( ECG machine ).

The recordings can be displayed on a moving graph paper or on a screen to give visual impression.

Cardiac cycle begins with impulses from the SA node.

The electrical impulses spreads through both atria causing atrial contraction(depolarisation ).

Atrial depolarisation -P wave

The electrical impulse is delayed for approximately 0.04sec at the AV node so that the atria have time to eject their contents into the ventricles-PR interval represents this delay.

The impulse then travels through the AV node & AV bundle down the bundle branch & through the purkinje fibres & the ventricles contract – ventricular depolarisation

Ventricular depolarisation - QRS complex

Ventricular repolarisation - T wave.

Total duration of depolarisation and repolarisation - QT interval.

U wave – non specific recovery after potential

NORMAL DURATIONS:

P wave - ≤ 0.11sec

P-R interval - 0.12-0.20 sec

QRS complex- ≤ 0.12 sec

QT interval - ≤ 0.42 sec

ECG CONVENTIONS & INTERVALS :

Depolarisation towards electrode – positive deflection.

Depolarisation away from electrode – negative deflection.

Sensitivity – 10 mm = 1 mV

Paper speed – 25 mm/sec

Each large ( 5mm ) square = 0.2 sec

Each small ( 1 mm ) square = 0.04 sec

Heart rate = 1500/ R-R interval (mm)

( 300/number of large squares btwn beats)

NORMAL VOLTAGE MEASURMENTS :

Voltage from the top of the R wave to the bottom of the S wave – 1 mV

Voltage of P wave – 0.1 -0.3 mV

Voltage of T wave – 0.2 – 0.3 mV

The standard external 12 lead ECG uses two sets of leads :

6 limb leads & 6 precordial (chest ) leads

6 limb leads divided into 2 :

1. Standard bipolar lead

2. Standard unipolar lead

Standard bipolar lead

Lead I - right arm & left arm

Lead II - right arm & left leg

Lead III - left arm & left leg

Standard unipolar lead :

VR –centre of heart and right arm

VL-centre of heart and left arm.

VF-centre of heart and left leg.

6 chest leads :

V1

V2

V3

V4

V5

V6

RECORDING OF ELECTRICAL IMPULSES :

Limb leads ( I,II,III,AVL,AVF,AVR ) record events in the frontal plane of the heart.

Chest leads ( V1,V2,V3,V4,V5,V6 ) record a horizontal view of the heart electrical activity.

CLINICAL VALUE OF ECG:

Interpretation of cardiac arrhythmias

Diagnosis of ischaemic heart disease

Assessment of ventricular hypertrophy

STANDARD BIPOLAR LEADS:

STANDARD UNIPOLAR LEADS:

CHEST LEADS:

CLINICAL IMPLICATIONS :

ECG abnormalities are categorized in to 5 areas

1) Heart rate

2) Heart rhythm

3) Axis or position of heart

4) Hypertrophy or increase in the size of the heart

5) Infarction / ischemia

TYPICAL ABNORMALITIES :

Pathologic rhythms

Heart conduction system disturbances

Myocardial ischemia

Myocardial infarction

CLINICAL IMPLICATION ASSOCIATED WITH WAVES,COMPLEX & INTERVALS OF ELECTROCARDIOGRAPHY :

I. P WAVE

Mean vector of normal atrial depolarisation is directed leftward & downward producing a positive ECG deflection.

NORMAL VALUE : 0.08-0.11 sec

CLINICAL IMPLICATIONS:

RA hypertrophy & LA hypertrophy

Primary intra atrial conduction abnormality

II. PR INTERVAL : Represents the time beginning of

atrial activation to the beginning of ventricular activation.

NORMAL VALUE : 0.12 – 0.20 sec CLINICAL IMPLICATIONS : Cardiac arrhythmiasIII. QRS COMPLEX : Ventricular excitation begins

predominantly in the middle third of the left side of inter ventricular septum .

Initial wave of depolarisation spreads through right side.

Resultant vector produces QRS deflection.

NORMAL VALUE : CLINICAL IMPLICATIONS : Right & left ventricular hypertrophy. Right bundle branch block

( prolonged QRS – >0.12 sec ,wide S wave).

IV. ST WAVE: Steady membrane

polarization from the end of depolarization to the beginning of repolarisation.

CLINICAL IMPLICATIONS:

Myocardial ischemia

ST segment depression

T wave inversion

Myocardial infarction

Tall T waves

ST segment elevation

v. Hypertrophy of heart

vi. Pulmonary infarction

vii. Altered K , Ca, Mg levels

viii.Pericarditis

ix. Ventricular hypertrophy

DRUGS THAT CHANGES ECG:o Quinidine

o Procainamide

o Amiodaroneo Quinineo Mefloquineo Halofantrineo Terfenadineo Astemizoleo Amitryptylineo Risperidoneo Propanololo Sotalol

o Penicillino Pentamidineo Erythromyci

no Amantadineo Doxorubicino Lithiumo Carbamazepi

neo Probucolo Cotrimazoleo Digoxino Verapamilo Diltiazem

AMBULATORY ECG MONITORING :

Also known as Holter monitoring.

During AEM patient wears a portable ECG recorder.

3 types of monitors are available.

Continuous monitor - record an ECG strip over the duration of the test.

Intermittent recorder - continuously monitor the ECG but only record preprogrammed abnormal ECG events.

Real time analytical recorder -record through out the monitoring period and analysis each beat as it occurs.

Monitors digitize , encode and store the information in a solid state memory or on a magnetic tape

Clinical values of ambulatory ECG includes

Aid to detect ,document ,characterize and evaluate arrhythmias and other ECG abnormalities.

ECG abnormalities include ST segment deviation , QRS complex ,PR intervals.

ECHOCARDIOGRAM :

Ultrasound imaging of the heart and allows the structures of the heart to be visualized as a two dimensional slice.

Transducer is held over the patient chest wall to produce an ultrasound.

Its an instrument that transmits high frequency sound waves.

ECHO is mainly based on the principle of reflection and refraction.

The ability of the ultrasonic beam to penetrate chest wall structures is inversely proportional to the frequency of the signal.

Helpful in detecting

-mitral stenosis

-heart diseases

-chamber enlargement

DOPPLER ECHOCARDIOGRAPHY

Depends on the principle that sound waves reflected from moving objects such as intra cardiac red blood cells undergo frequency shift.

The greater the frequency faster the blood is moving.

Used for studying the pressure changes on either side of the valve & abnormal directions of blood flow.

TRANSOESOPHAGEAL ECHOCARDIOGRAPHY :

An ultrasound probe in the shape of an endoscope is passed into the oesophagus and positioned immediately behind the left atrium.

Helps in detecting *patient with valve dysfunction. *congenital abnormalities . *patient with systemic embolism.

CARDIAC CATHETERISATION :

It involves passing a catheter into the right or left side of the heart.

Right sided heart catheterisation helps to detect oxygen saturation in different chambers.

Left heart catheterisation helps to assess coronary artery diseases.

Mild sedative is given prior to test.

Procedure takes 90 mins to 3 hrs.

Radio opaque contrast material & indicator solutions can be injected via the catheter.

ANGIOGRAPHY :

Medical imaging technique in which an X ray image is taken to visualize the inside of blood vessels and organs of the body.

A catheter is inserted into the artery ,a radio opaque dye is injected with the aid of fluoroscopy allowing the imaging of blood vessels.

Used to detect lesion that occlude the vessels.

COMPUTED TOMOGRAPHY :

Rarely used.

More expensive.

Non invasive method.

Used to detect congenital heart diseases.

Useful in imaging the chambers of the heart , great vessels ,pericardium.

Chamber size and volume can also be measured.

MAGNETIC RESONANCE IMAGING :

Very expensive. Technician places a small sticky

electrode patches on your chest and back.

These electrodes are attached to ECG monitor.

Used for detecting -CHF -MI

RADIOLOGY :

Chest radiograph is useful for determining the size and shape of the heart.

Cardiothoracic ratio should be less than 0.5.

Transverse cardiac diameter should be less than 15.5cm.

RADIONUCLIDE IMAGINGGamma emitting radionuclide with a short half life.

Gamma rays are detected by means of a planar or tomographic camera.

Blood pool imaging.

Myocardial perfusion imaging.

BLOOD POOL IMAGING :

The isotope is injected intravenously and mixes with the circulating blood.

The gamma camera detects the amount of isotope emitting blood in the heart at different phases of the cardiac chambers.

By linking the gamma camera to the ECG it is possible to collect information over multiple cardiac cycle.

MYOCARDIAL PERFUSION IMAGING :

This technique involves obtaining scintiscans of the myocardium at rest & during stress after the administration of an intravenous radioactive isotope such as thallium.

REFERENCES:PHARMACOTHERAPY –A PATHOPHYSIOLOGIC APPROACH-JOSEPH T DIPIRO.

DAVIDSONS PRINCIPLES AND PRACTICE OF MEDICINE-CHRISTOPHER HASLET-19th ed

MEDICAL SURGICAL NURSING –SHAFER 5th ed

ESSENTIALS OF PHARMACOTHERAPEUTICS-F.S.K BARAR-4th ed.

A MANUAL OF LABORATORY & DIAGNOSTIC TESTS –FRANCES FISCHBACH , 8th ed.

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