Cardiology Week 4 Summary

Question 16

How do you rate intensity of heart murmurs?

By tradition, murmurs are graded on a scale of 1 to 6 which was initially a research tool used for the study of systolic murmurs (Freeman & Levine, 1993) and is known as the Levine system.

Levine system was initially developed for classifying benign vs. pathological (grade 3 or more) murmurs. However, there are limitations in terms of reproducibility and inter-rater reliability. More recently, it has been shown using heart sounds as an internal reference improved the reproducibility (Keren et al.)

Freeman AR, Levine SA: Clinical significance of systolic murmurs: Study of 1000 consecutive “noncardiac” cases. Ann Intern Med 6: 1371-1379. 1933.

Keren R, Tereschuk M, Luan X. Evaluation of a novel method for grading heart murmur intensity. Arch Pediatr Adolesc Med. 2005 Apr; 159(4):329-34.

Question 17

What is the Canadian Cardiovascular Society (CCS) classification for angina?

Developed for grading of angina pectoris …

1. Asymptomatic
2. Can walk more than 2 blocks or up 1 flight of stairs
3. Can walk less than 2 blocks or up 1 flight of stairs
4. Pain at rest
   Class IV is further classified into …
   1. Pain resolved with intensified medical therapy, now stable on oral medication
   2. On optimal oral therapy with pain still occurring minimal provocation
   3. Pain monitoring and parenteral medications and/or intra-aortic balloon counterpulsation

It was originally described in a letter to the editor published in Circulation and subsequently adopted clinically and in many clinical trials.

Campeau L. Grading of angina pectoris(Letter). Circulation. 1976;54:522-523.

Question 18

What is the Killip classification for acute myocardial infarction and the associated in-hospital mortality?

Based on a series of New York patients with acute myocardial infarction reported in one of the first CCU in North America. Over the years the mortality of patients have improved but the mortality of class IV patients remains high. This classification remains useful today as it is simple and based primarily on physical examination and still provides useful information for triaging patients.

Killip T, Kimball JT. Treatment of myocardial infarction in a coronary care unit: a two year experience with 250 patients. Am J Cardiol 1967; 20:457-64

Question 19

What are the causes for short RP and long RP interval in narrow complex SVTs?

1. Short RP (R-P < 50% of the R-R interval)
   1. Typical AVNRT
   2. Orthodromic macroentry over accessory pathway
   3. Atrial tachycardia with first degree AV block
2. Long RP (R-P >50% of the R-R interval)
   1. Atrial tachycardia
   2. Sinus node reentrant tachycardia
   3. Atypical AVNRT:
      • Down the “fast” AV node pathway & retrograde conduction up the “slow” pathway
3. Orthodromic SVT with prolonged V-A conduction
   • Slowed conduction over accessory pathways
   • More common as increased frequency of EP ablation for AVNR

Question 20

What are the causes of prolonged QT interval?

The QT interval is prolonged when the corrected QT interval (QTc) is more than 440 msec in men and 460 msec in women.

Idiopathic long QT interval syndrome:

1. The Jervell-Lange-Nielson Syndrome: Accompanied by sensorineural deafness. Autosomal recessive.
2. The Romano-Ward Syndrome: Autosomal dominant
3. Sporadic long QT Syndrome
   • (5% per year risk for syncope, symptomatic patients 10 year mortality rate = 50%)
   • Syncope due to torsades de points polymorphic v tach, triggered by adrenergic arousal.

Secondary(acquired) types of QT interval prolongation:

1. Coronary artery disease – myocardial ischemia and infarction (most common, QT interval is an independent risk factor post MI)
2. Metabolic disturbances – electrolyte imbalance; e.g. hypocalcemia, liquid protein diet, intracoronary contrasts
3. Cardiac drugs – quinidine, procainamide, disopyramide, propafenone, sotolol, amioderone
4. Psychotropic drugs – phenothiazines, tricyclic antidepressants
5. Antihistamine – terfenadine overdose or used in combination with antifungal agent e.g. ketoconazole or erythromycin
6. Pentamidine used in AIDs
7. Central nervous system, esp. intracranial hemorrhage
8. Autonomic nervous system dysfunction secondary to radical neck dissection, carotid endartectomy, transabdominal truncal vagotomy
9. Mitral valve prolapse, cardiomyopathy
10. Misc. – severe bradycardia, high degree AV block, post Stroke-Adams seizures, hypothyroidism, hypothermia, pheochromocytoma, organophosphate poisoning.