cardiovascular system-diagnostic tools
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Transcript of 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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