cardiovascular system-diagnostic tools

DIAGNOSTIC TOOL BY KAPIL MOHAN 7TH BATCH,INTERN JMCTH

CVS

TYPES1. Ecg2. Non invasive cardiac imaginga. echocardiographyb. nuclear cardiologyc. mri/ct imaging3. Diagnostic cardiac catheterization & Coronary angiography

ECG/EKGGraphical recording of electric potentials generated by heart, signals detected by means of metal electrodes attached to extremities and chest wall.Clinincal utility: Immediate, noninvasive, inexpensive, highly versatile test

ECG LEADS12 conventional ECG leads are there divided into two groups : 6 limb leads (extremity) 6 chest leads ( precordial )Limb leads record potentials transmitted onto frontal plane and chest leads record potentials transmitted onto horizontal plane.

Ecg leads are configured so that +ive(upright) deflection is recorded if wave of depolarisation spreads towards postive pole of lead and –ive deflection is recorded if wave spreads towards negative pole.

EINTHOVEN TRIANGLE The 3 standard limb leads form an

equilateral triangle at centre of heart.

GENESIS OF ECG

P wave QRS complex T wave U wave

RHYTHM OF HEART Normal rhythm is sinus rhythm. Cardiac pacemaker: SA node (60-100

bpm) Other potenial pacemakers are known

as ectopic or subsidary pacemakers atrial/junctional pacemaker- 40-60bpm Ventricular pacemaker:20-40bpm

IRREGULARITYRegeularly irregular- premature beats during any rhtyhm , bigeminal rhythmIrregularly irregular – atrial fibrillation( disrete p waves of sinus rhythm are replaced by numerous, small fibrillating waves.Ventricular fibrillation- rapid small deformed deflections

R-R INTERVAL- HEART RATE Heart rate- number of heart beats /

min. In ECG- number of cardiac cycles

occuring during a 60 sec continuos recording of ecg.

Method: 300/ no. of large squares between two R waves.

P WAVE Produced by atrial depolarisation Normally upright in most of ecg leads

except avR ( dirction of atrial activation is away from this lead )

Height : < 0. 25 mv width : < 0.10 sec

ABNORMALITIES OF P WAVE Absentatrial fibrillation atrial flutter( saw toothed apperance of baseline) venticular tacycardia Hyperkalemia Broad p wave left atrial enlargement >0.10 sec

Inverted p wave junctional rhythm by pass tract Tall p wave right atrial enlagement p pulmonale (pulmonary hypertension) p congenitale ( congenital heart disease )

QRS COMPLEX Produced by ventricular depolarisation, r wave is

positive while q and s waves are negative Q wave – seen in L1, aVL, V5, V6 (physiological) width:<0.04sec, depth <25%of R wave pathological q wave due to necrosis of heart muscle or MI and criteria is ≥0.04 sec , >1/4 of R wave, +nt in other leads than in those with normal q waves

R wave : almost all the leads except

aVR. Gradually increases as we move from V1 to V6(V1 ≤0.4 mV ; V6 ≤2.5 mV) Abnormalities : tall R wave In V1 lead: rvh, rbbb, wpw syndrome, true posterior wall infarction In V6: lvh, lbbb

S WAVE Negative deflection that follows R

wave. Normally greater than R wave in V1:

smaller than R wave in V6

ABNORMAL QRS COMPLEX Normal width : 0.04 sec to 0.08 sec >0.08 sec Bundle branch block: rbbb, lbbb Intraventricular conduction defect:

antiarrhythmic drugs eg amiodarone, electroltye imbalance eg hyperkalemia, myocardial disease eg myocarditis

Ventricular preexcitation : wpw syndrome, lgl syndrome

Wide QRS arrhythmias :atrial fibrillation with VT

T WAVEProduced by ventricular depolarisation Normally upright in most leads . Inverted in aVR along with inversion of P wave and QRS complexAlso in lead V1, V2, V3, L3Amplitude : ≤5mm in limb leads; ≤ 10mm in precordial leads.

Abnormalities of T wave Inverted T wave : physiological- heavy metals, smoking, anxiety, tachycardia, hyperventilation extracardiac causes- systemic ( shock, haemorrhage), cranial (CVA) , abdominal (pancreatitis, cholecystitis), respi ( pulmonary embolism ), endocrine ( hypothyroidism)

Specific causes- 1º abnormality- pharmacological

(digitalis),metabolic(cardiomyopathy), pericardial( pericarditis, pericardial effusion ), ischaemic ( infarction, coronary insufficiency)

2º abnormality- venticular hypertrophy, bbb, wpw syndrome

THE INTERVALS P-R interval Q-T interval

P-R INTERVAL From onset of P wave to beginning of

QRS complex. Normal PR interval – 0.12 – 0.20 sec

ABNORMALITIES OF PR INTERVAL Prolonged PR interval >0.20 sec Indicates increased AV nodal conduction delay or 1st degree AV block. Causes- vagal domination in athelets, ARF, CAD, drugs acting on av node eg digitalis, CCBs

Reduced PR interval Causes- AV nodal or junctional rhthym,

wpw syndrome with pre-excitation Variable PR interval causes- type 1 , 2nd degree av block,

complete av block, wandering pacemaker rhtyhm

AXIS DEVIATION Right axis deviation Left axis deviation

RIGHT VENTRICULAR HYPERTROPY Criteria for diagnosis R wave in V1 :> 4mm R:S in V1:>1 S wave in V6 >7mm R in V1+ S in V6: >10 mm

CAUSES OF RVHPulmonitary HTNCongenital heart diseaseChronic cor pulmonalePulmonary valve stenosisIsolated congenital PSPS of TOF

LEFT VENTRICULAR HYPERTROPHY Voltage criteria S in V1 or V2+ R in V5 or V6 >35 mm

(sokolow) R in V5+V6>25 mm; R in aVL >11 mm

(framingham) S in V3+ R in aVL >28 mm (men ),

>20mm (women ) (cornell)

CAUSES OF LEFT VENTRICULAR HYPERTROPHY

Systolic LV overload- systemic HTN, AS (valvular, subvalvular), coarction of aorta, HOCM

Diastolic LV overload –AR, MR,VSD,PDA

NON INVASIVE CARDIAC IMAGING Echocardiography Nuclear cardiology MRI/CT imaging

ECHOCARDIOGRAPHY Types 2D Doppler Stress Transesophageal

2D ECHOCARDIOGRAPHY Principle-ultrasound reflection off

cardiac structures to produce images of heart.

For TTE (transthoracic ) echocardiogram, imaging is performed with a handheld transducer placed directly on chest wall

Advantage – instantaneous images of cardiac structures is obtained for interpretation

Ideal for cardiac emergencies.

Useful in LV hypertrophy Hypertropic cardiomyopathy Valve abnormalities – gold standard .

ex- MS Pericardial disease – modality of choice

for pericardial effusion. Intracardiac masses. Appear as echo

dense strutures.

DOPPLER ECHOCARDIOGRAPHY Principle:uses ultrasound reflecting off

moving rbc to measure the velocity of blood flow across valves, with cardiac chambers and through great vessels.

Different color indicates different direction of blood flow

Red towards and blue away from transducer with green superimposed when there is turbulent flow.

Modified Bernoulli equation: Pressure change=4 times (velocity)² High velocity of blood flow directed

along the line of doppler beam is measured such as in valve stenosis, valve regurgitation, or intracardiac shunts.

These high velocities are used to determine intracardiac pressure gradients

STRESS ECHOCARDIOGRAM 2D and Doppler are usually performed with

patient in resting state. Further information can be obtained by reimaging during either exercise or pharmacologic stress.

Indications – confirm suspicion of IHD and determine extent of ischaemia.

Exercise testing done using either upright treadmill or bicycle, pharmacologic testing by infusion of dobutamine.

TRANSESOPHAGEAL ECHOCARDIOGRAM Used when limited information is

obtained from TTE, TEE is useful. Used for Diseases of aorta- aortic dissection Atrial thrombi Patent foramen ovale Presence of vegetations in infective

endocarditis

NUCLEAR CARDIOLOGY Nuclear (or radionuclide ) imaging requires

iv administration of radiopharmaceuticals ( isotopes or tracers )

Once injected , isotope traces physiologic process and undergoes uptake in specific organs. Radiation is emitted in form of photons, generally gamma rays.

Special camera detects these photons and creates images via computer interface

Most commonly used technologies are 1. SPECT (single photon emission

computed tomography ) 2. PET ( positron emission

tomography ) Both differ in intrumentation,

acquisition, resolution and nuclides used.

MRI IMAGING Principle- based on magnetic properties of

hydrogen nuclei. Larger vessels can be visualised on mri

without contrast agents, gadolinium is frequently employed as contrast agent to produce magnetic resonance angiograms.

Both static and cine images can usually be obtained using electrocardiographic triggering, often within short breadth holds of 10-15secs.

MRI is of great value in defining anatomic relationships in patients with complex congenital heart disease and cardiomyopathies

CT SCAN Fast simple, noninvasive technique that

provide images of myocardium and great vessels with excellent spatial resolution and good soft tissue contrast.

Important clinical applications Pericardial calcification Cardiac masses, particularly those containing

fat or calcium. Suspected arrhythmogenic right ventricular

dysplasia

Suspected pulmonary embolism –examination of choice.

Aortic dissetion

INVASIVE CARDIAC IMAGING Types: Cardiac catheterization Coronary angiography

Both are indicated to evaluate the extent and severity of cardiac disease in symptomatic patients and to determine if medical, surgical, or catheter based interventions are warranted

.

TECHNIQUES Dependent upon patient’s symptoms and clinical

condition with some direction provided by noninvasive studies.

Vascular access- percutaneous technique used to enter femoral artery and vein as the preferred access site for left and right heart catherterization , respectively.

Flexible sheath is inserted into vessel over a guidewire, allowing diagnostic catheters to be introduced into vessel and advance towards heart using fluroscopic guidance.

Other blood vessels being used are- Brachial or radial artery- (normal allen’s test confirming dual

blood supply to hand from radial and ulnar arteries is prerequisite to access this site.

Hemodynamics –shape and magnitude of pressure wave forms provides important diagnostic information.

In absence of valvular heart disease, atria and ventricles are “one chamber” during diastole when tricuspid and mitral valves are open while in systole when pulmonary and aortic valves are open, ventricles and their respective outflow tracts are considered “one chamber”.

When aortic stenosis is present , there is systolic pressure gradient between left ventricle and aorta.

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