Lec 27 Cardiology Diagnostics: Advanced Non-Invasive

Question 1

Most important of the epicardial arteries; supplies the left and right sides of the heart:

Answer 1

Left Coronary Artery

Question 2

Gold standard for diagnosis of Coronary Artery Disease

Answer 2

Coronary Angiography

Question 3

Luminal remodeling of the coronary artery wherein plaque invades the intima of the vessels cannot be seen in Coronary Angiography. This imaging modality is used instead:

Answer 3

Intraluminal ultrasound

Question 4

(T/F) Most patients presenting with chest pain in the

emergency room showed no worrisome ECG and no history of CAD.

Answer 4

TRUE.

Question 5

(T/F) A depressed ST segment suggests Transmural (epicardial) injury.

Answer 5

FALSE.

With predominant subendocardial ischemia, the resultant ST vector will be directed toward the inner layer of the affected ventricle and the ventricular cavity. Overlying leads therefore will record ST DEPRESSION.

With ischemia involving the outer ventricular layer (transmural or epicardial injury), the ST vector will be directed outward. Overlying leads will record ST ELEVATION.

Question 6

An Inotropic/Chronotropic pharmacologic stress agent that is used to attain maximal HR.

Answer 6

Dobutamine

o Increase the dose to attain maximal HR

• Inotropic - can change the forces of muscle contraction
• Chronotropic - can change heart rate

Question 7

An Alpha-2 adrenergic specific agonist used as a vasodilator in pharmacologic stress-testing

Answer 7

Regadenoson

Question 8

Indications for Pharmacologic Stress Testing:

Answer 8

1. Inability to exerciseo Physical limitations (amputations, etc.)o Recent operationso Comorbidity
2. Limited exercise capacityo Deconditioning/ poor motivationo Limiting physical conditions (COPD, claudication)

Question 9

Unmasks imbalance between oxygen demand and supply:

Answer 9

Coronary Flow Reserve

• In a normal patient, there are 3 levels of resistance in coronary blood flow (such as diagonal coronaries) before reaching the myocardium. A stenosis at rest would result
  to compensatory dilatation of the coronary arteries to increase blood flow. But if the stenosis is severe, this
  compensatory mechanism won’t be enough.
• During stress, instead of simply dilating the arteries, part of the myocardium affected by the stenosis would use up the blood reserve. This limits any additional perfusion of the said myocardium.

Question 10

Resting ECG Findings which can give a false positive stress test:

Answer 10

1. Ventricular hypertrophy
2. Pre-excitation syndrome
3. Left bundle branch block
4. > 1 mm of resting ST segment depression
5. Digitalis use
6. Paced ventricular rhythm
   * If the patient have any of these, don’t do just the treadmill stress test since it will be inconclusive: Incorporate imaging modalities

Question 11

Imaging modalities for perfusion abnormalities:

Answer 11

SPECT/PET/CCTA/

SPECT - Single Photon Emission Computed Tomography
PET - Positron Emission Tomography
CCTA - Coronary Computed Tomography Angiography
CMRI - Cardiac MRI

• Echocardiography and CMRI only detect systolic dysfunction, which is already in the late stage of ischemia.

Question 12

Radioactive tracers used in SPECT:

Answer 12

1. Thallium-201
      Potassium-making
      Half-life: 3 days
      Has low photon energy 
      cannot be used for obese patients and patients with   pendulous breasts (low resolution)

2. Technitium-99 setamibi/tetrofosmin
    Half-life: 6 hours
    Has higher photon energy compared to Thallium-201

Question 13

Radioactive tracers used in PET

Answer 13

(RON)

1. Oxygen-15 water
2. Nitrogen-13 ammonia
3. Rubidium-82 chloride
4. Fluorodeoxyglucose (FDG)
    Used to assess cellular metabolism only and detect viable muscles (i.e. how the muscles use glucose)
    Does not measure blood flow unlike the other three tracers

• Oxygen, nitrogen, and rubidium are used for perfusion studies to measure blood flow

Question 14

Identify the coronary artery supplying the following parts of the heart:

Anteroseptal:

Inferoseptal:

Lateral Left Ventricle:

Answer 14

Anteroseptal area supplied by Left Anterior Descending (LAD)

Inferosepatal area by Right Coronary Artery (RCA)

Lateral left ventricle by Left Circumflex Artery (LCX)

Question 15

The decreased specificity of SPECT is due to:

Answer 15

Soft Tissue Attenuation

• Attenuation - general term that refers to any reduction in the strength of a signal

o Need for attenuation corrections

Question 16

Interpret the following myocardial perfusion findings:

Rest: Normal
Stress: Abnormal

Answer 16

ISCHEMIA

• Abnormal scans present only during stress and none at rest.
• For myocardial infarction, abnormal scan during both rest and stressed states

Question 17

(T/F) SPECT has high sensitivity but low specificity.

Answer 17

TRUE. SPECT is sensitive (91%) in detecting CAD. However, since it can detect artifacts, it can yield false positives, making it less specific (low specifictiy) but still better than a treadmill stress test which has both low sensitivity and low specificity.

Question 18

A Nuclear Imaging modality that needs a cyclotron or generator to produce the tracers and is very expensive (60,000php)

Answer 18

PET Scan

Question 19

(T/F) Mismatching metabolism patterns in PET perfusion suggests a viable myocardium and that revascularization
results in recovery of myocardial function.

Answer 19

TRUE.

Reduced blood flow + preserved or enhanced FDG
uptake (mismatch)*

Normal or near normal blood flow + reduced FDG
uptake (reserved mismatch)*

• Remember that Fluorodeoxyglucose (FDG) is used to assess cellular metabolism only and detect viable muscles (i.e. how the muscles use glucose). A mismatch therefore signifies a form of adaptation in the cells: increased FDG uptake for cells when blood flow is reduced and vice-versa
• Matching patters indicate a non-viable myocardium:

  >Reduced blood flow and reduced FDG uptake (match) 
  
  >Mild to moderate reduction in blood flow and FDG uptake (match)

Question 20

Greater than what percentage of the myocardium should be ischemic in patients in order to benefit more from revascularization (angioplasty, bypass surgery) than medical therapy?

Answer 20

> 12.5%

if <12.5% ischemic myocardium - maximal medical therapy is better

Question 21

In this modality, image production relies upon magnetic fields created by superconducting magnets and sophisticated electronics which manipulate and process the radiofrequency energy. It also emits no harmful ionizing radiation.

Answer 21

Magnetic Resonance Imaging

Question 22

Basic Cardiac MRI procedure:

Answer 22

1. Remove first metallic materials (patient with metal pace-makers and metal implants cannot undergo MRI).
2. Then, ECG leads are attached, and the patient is positioned in the gantry, where he/she will stay there for an hour.

Question 23

The gold standard for assessing right and left ventricular function

Answer 23

Cardiac MRI

o Can view the myocardium in isolation, without the valves and other structures (unlike 2D echo)

o Very accurate measurements

Question 24

Drug used in conjunction with CMR to assess contractility of heart muscles and presence of wall motion abnormality at maximum dose.

Answer 24

Dobutamine (Dobutamine Stress CMR)

Question 25

Contrast material (for CMRI) used to assess viability of myocardium. It is easily excreted out from the extracellular space in normal myocardium, but accumulates in infarcted myocardium. Therefore, the infarcted segments will light up.

Answer 25

Gadolinium (Late Gadolinium Enhancement)

• 10-15 minute waiting time after injection before doing procedure

Question 26

What percentage of transmurality of LGE predicts recovery in function?

Answer 26

< 25% transmurality best predicts recovery in function

LGE > 75% transmurality predicts non-viability: these patients will not benefit from revascularization such as CABG or PTCA.

• Remember: sa normal myocardium, madali lang maexcrete ang gadolinium pero nag-aaccumulate sa infarcted myocardium meaning, lower transmurality, lesser extent of infarction
• Gadolinium based contrast with severe kidney disease (GFR <30 mL/min/ 1.73 meter squared) is contraindicated due to the risk of systemic nephrogenic fibrosis

Question 27

Latest tool for diagnosis of CAD

Answer 27

Cardiac CT Angiography

Question 28

CAC Score for mild plaque burden in the Calcium Scoring used in CCTA.

Answer 28

CAC score Calcified Plaque Burden

0 - No identifiable atherosclerotic plaque

1-10 - Minimal plaque burden

11-100 - Mild plaque burden

101-400 - Moderate plaque burden

401-1000 - Severe plaque burden

> 1000 - Extensive plaque burden

Question 29

CCTA Triple rule-out for Coronary Artery Disease:

Answer 29

 CAD

 Pulmonary embolism

 Aortic dissection