Basic principles of stress tests

Imaging methods in

cardiovascular medicine

Miloslav Špaček, MD

• Introduction!

• Basic principles of stress tests!

• Exercise ECG!

• Transthoracic echocardiography!

• Transesophageal echocardiography !

• Stress echocardiography!

• Nuclear imaging methods!

• Computed tomography!

• Magnetic resonance imaging !

• Invasive diagnostic methods

Introduction

• dynamic part of cardiology

• principles and limitations !

• multidisciplinary cooperation !

• specific cardiac projections

• morphology vs. function

Basic principles of stress tests

• detection of ischemia

• detection of viable myocardium

• estimation of exercise tolerance

• evaluation of prognosis

• sensitivity vs. specificity

ISCHEMIC CASCADE

Increse in exercise

Insufficient perfusion

Anaerobic metabolism

Diastolic dysfunction

Decreased contractility

ECG changes

Clinical symptoms

• Pretest probability of CAD ?

• Baseline ECG changes ?

• Patient able to exercise ?

• Pretest probability of CAD ?

• ! Intermediate !!

• Baseline ECG changes ?

• STD (LVH) / LBBB / WPW / DIG / TKS !

• Patient able to exercise ?

• adenosin / dipyridamol /// dobutamin

• evidence of impaired myocardial perfusion

• and/or impaired myocardial contractility

!

• 17-segment model

• polar maps ("bulls eye")

Exercise ECG test

• easily available, low-cost

• treadmill / bicycle

• increasing workload protocols (á 2-3 min)

• ECG + BP + clinical symptoms

• target: 85% x (220-věk)

• target HR reached (220-age) x 85%

• limiting symptoms (chest pain, dyspnea, claudication, exhaustion)

• > 250/115 mmHg

• severe hypotension

• severe arrythmias

• exhaustion / inability to maintain exercise

• STE

• horizontal / descending STD>1mm

• ( T-wave inversion / ascending STD )

!

• sensitivity: 45 - 50% , specificity 85 - 90%

Transthoracic echo

• versatile

• low-cost

• readily available

• no radiation

• -> primary dg. method for most cardiac pathologies

• Probes >1MHz, 1500m/s

• (M-mode) x 2D x 3D

• Doppler (CW x PW x CFM x TDI)

!

• Contrast echo imaging

Aortic regurgitation

Impaired relaxation

• Bernoulli equation P = 4v² [mmHg],

• Continuity equation A1 x v1 = A2 x v2

Transesophageal echo

• Same principle as in TTE

• Shorter distance ("region of interest")

• Lower signal attenuation

• 5-7,5 MHz

• Perioperational TEE

• Valvular pathologies

• Intracardiac shunts

• Intracardiac mass

• Infective endocarditis + complications

• Prosthetic valve dysfunction

• Congenital cardiac disease

• Aortic dissection

• Monitoring of structural heart disease procedures

• Insufficient TTE images

Stress echo

• detection of ischemia

• viability testing

• severity of valvular disease (Ao / Mi stenosis)

• contractile reserve testing!

• (pulmonary hypertension)

• low-cost !

• morphologic data !

• sensitivity 79-83%, specificity 84%

!

• insufficient acoustic window (rare with contrast)

• ergometr x dobutamin (up to 40ug/kg/min)

• same targets as in stress ECG

• ischemia = impaired / delayed contractility

• high-risk if ≥3 segments impaired

• viability= biphasic response (2-10ug/kg/min)

Nuclear imaging

methods

• gamma rays (decay of radionuclids)

• impaired perfusion, viability testing, LV function

• robust prognostic value based on large data

SPECT PET

Technecium 99

13N- ammonium Rubidium 82

18Fluordeoxyglucose

• reconstruction of data to 3 tomographic projections (HLA / VLA / SA)

• 17 segment model + polar maps

• relative impairments of perfusion

• triggering

• one-day (session) / two-day (session) protocols

• ergometr / dipyridamol / dobutamin

• low spatial resolution (NB: arrythmias !!)

• sensitivity 73-91% , specificity 80%

• coincidence detection

• pozitrons -> gamma rays

• viability (FDG)

• perfusion-metabolic mismatch

!

• high-cost !

Computed

tomography

• morphologic imaging

• CT coronary angiography

• calcium score

Prospective vs. retrospective triggering

• back projection of raw data

• any projection possible

• high spatial resolution (1,5-2mm)

• strong negative predictive value!

!

• radiation exposure!

• risk of contrast nephropathy!

Magnetic resonance

imaging

• versatile method - morfology + function + (perfusion)

• detection of energy released during proton relaxation

• different morphologic sequences (T1 - fat, T2 - water)

!

• time-consuming

• high-cost

• claustrophobia, metal

• not suitable for coronary morphology

Fire & forget - no possibility of back projection!!!!

ECG and respiratory triggering

Late gadolinium enhancement

• adenosin x dobutamin

• “first-pass” gadolinium

Invasive diagnostic

methods

• morphology of heart chambers and aorta

• morphology of coronary arteries

• direct blood pressure measurements

• immediate therapeutic options

!

• specific complications (most commonly bleeding)

1Fr = 1/3mm

4-8Fr

• 50 000 CAG/year in CZ “luminogram”

• iodine contrast agents

• femoral / radial approach

Aortography (thoracic)

Ventriculography (tako-tsubo)

IVUS (20 MHz)

OCT (10um)

NIRS - IVUS

Fractional flow reserve - comparison of blood pressure in aorta and distal to stenosis following administration of

vasodilator (adenosin).

• blood pressure sensor at the tip of catheter for

direct BP measurement

• detection of shunts (ASD...)

• Cardiac Output

measurement (Fick/

termodilution) Swan-Ganz catheter

(A-V x CO = O2 consumption)

Thank you for your

attention