Cardiology Week 2 Summary

Question 6

What is the hemodynamic (Forrester) classification in acute myocardial infarction?

In 1977, Forrester et al. proposed the use of right heart catheterization (RHC) in acute myocardial infarction AMI and classified patients into four invasive subsets based on cardiac index (CI) and pulmonary artery wedge pressure (PWP) values.

Threshold values for PWP and CI were 18 mm Hg and 2.2 L/min/m, heralding imminent pulmonary edema and cardiogenic shock, respectively. It predicted the in-hospital mortality independently of the patient’s age, gender, precipitating factors, and AMI location.

Forrester J, Diamond G, Chatterjee K, et al. Medical therapy of acute myocardial infarction by application of hemodynamic subsets (first of two parts). N Engl J Med. 1976; 296:1356-1362.

Siniorakis E, Arvanitakis S, Voyatzopoulos G, et al. Hemodynamic Classification in Acute Myocardial Infarction. Chest 2000; 117; 1286-1290.

Question 7

What are the conditions apart from acute coronary syndrome (ACS) associated with troponin elevation?

1. Myocarditis
2. Pulmonary embolism
3. Subarachnoid haemorrhage
4. Heart failure
5. Extreme exercise
6. Supra-ventricular tachycardia
7. Kawasaki disease
8. Heart transplantation
9. Direct cardiac trauma
10. Cardioversion / defibrillation
11. Chemotherapy
12. Cancer
13. Antibody that cross react to the troponin assay

Question 8

If the JVP is 8 cm above sternal angle at 45%, what is the estimated right atrial (RA) pressure / CVP (central venous pressure) in mmHg?

VP in mmHg = (JVP + 5 cm) / 13.5 * 10

It is useful to convert the height of JVP estimated in cm to right atrial pressure in mmHg:

1. It corresponds to the pressure measured by pulmonary artery catheter/Swan Ganz.
2. Echocardiographer use the RA pressure in mmHg to estimate the RV systolic pressure by adding this number to the estimated gradient between right atrium and right ventricle (e.g. by tricuspid regurgitation jet)

Method:

1. You have to add 5 (the cardiology constant) because of the distance from the Angle of Louis to the middle of the right atrium.
2. Then divide by 13.5 as this is how many times mercury is denser than water
3. Multiply by 10 to convert cm to mm

Question 9

Which are the clinical findings of significant aortic stenosis? How can you estimate the degree of severity?

1. Cresendo-decresendo systolic murmur with left ventricular hypertrophy
2. Right mid-clavicular amplification
   Radiates along the sash which passed anteriorly from right mid-clavicular area down over aortic valve area, further down to the apex, and to the 5th and 6th ICS in the anterior and mid-axillary lines, but not into the axilla.
3. Severe cases cause paradoxical splitting
4. Carotid shudder (in patients with severe aortic stenosis and severe aortic insufficiency)
5. Parvus-et-tardus carotid upstroke
6. Maneuver
   1. Handgrip which increase the murmur exclude AS
   2. Murmurs tend to increase after a long diastole or amyl nitrite
7. Degree of severity can be estimated by …
   1. Late peaking of murmur
   2. Diminished or absent S2
   3. Estimating the interval between the peak PMI (felt with the right hand) and the peak of the carotid artery upstroke (felt with the left hand). These are separated in proportion to the severity of the stenosis.

Question 10

What is the contemporary definition of myocardial infarction?

For many years, the diagnosis of acute MI relied on the revised criteria established by the World Health Organization (WHO) in 1979. Two of these criteria were required for diagnosis of an acute STEMI:

• Chest discomfort characteristic of ischemia
• Typical ECG pattern including the development of Q waves
• Typical elevations in serum markers of myocardial injury, usually creatine kinase (CK)-MB

Patients with typical chest pain, no evidence of ST elevation or Q waves, and elevated CK-MB would have an NSTEMI. In comparison, patients with an unstable pattern of chest pain, possible ECG changes of ischemia but no ST elevation or Q waves, and normal CK-MB would have UA.

However, this definition of MI is too restrictive. Many patients with an acute MI have no recognizable symptoms, a substantial number have an ECG that reveals only nonspecific changes or may even be normal, and some patients have normal serum CK-MB but elevated troponins. According to the WHO criteria above, a patient with ischemic symptoms, no ST elevation, and a normal serum CK-MB but elevated serum troponins would be considered to have UA.

As a result of these limitations, a joint European Society of Cardiology (ESC) and American College of Cardiology (ACC) committee proposed the following definition of an acute, evolving, or recent MI in 2000: Typical rise and gradual fall (troponin) or more rapid rise and fall (CK-MB) of biochemical markers of myocardial necrosis with at least one of the following:

• Ischemic symptoms
• Development of pathologic Q waves on the ECG
• ECG changes indicative of ischemia (ST segment elevation or depression)
• Coronary artery intervention (eg, angioplasty)