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Iran Specialty Board - Cardiology study materials
Iran Specialty Board - Cardiology study resources

Iran Specialty Board - Cardiology: Basic Cardiovascular Sciences and Research Methodology

Iran Specialty Board - Cardiology · Work through your exam, one topic at a time.

All guide sections

Basic Cardiovascular Sciences and Research Methodology

This domain tests physiological principles that explain clinical findings and the biostatistics needed to interpret trial results and diagnostic studies; items reward understanding rather than formula recall.

Physiology

  • Cardiac action potential: phase 0 sodium influx, phase 1 transient potassium efflux, phase 2 L-type calcium influx, phase 3 potassium efflux, phase 4 resting potential; the SA node uses the funny current for spontaneous depolarisation.
  • Laplace law: wall stress equals pressure times radius divided by twice thickness; this explains why dilated ventricles and thin-walled atria are prone to arrhythmia and rupture.
  • Poiseuille law: flow is proportional to the fourth power of the radius, so small changes in vessel calibre cause large resistance changes.
  • Fick principle: cardiac output equals oxygen consumption divided by the arteriovenous oxygen difference; Gorlin formula derives valve area from flow and gradient.
  • Frank-Starling relationship describes increased stroke volume with increased preload until overload occurs.

Statistics

  • Sensitivity is true positives divided by true positives plus false negatives; specificity is true negatives divided by true negatives plus false positives.
  • Positive predictive value depends on prevalence and falls as prevalence falls.
  • Likelihood ratio: positive LR equals sensitivity divided by one minus specificity.
  • NNT is the reciprocal of the absolute risk reduction.
  • Type I error is alpha (false positive); power is 1 minus beta, conventionally 80%.
  • Intention-to-treat analysis preserves randomisation; per-protocol analysis can overestimate benefit.

Worked example

In a study of 200 patients, 90 of 100 with disease test positive and 20 of 100 without disease test positive. Sensitivity is 90%, specificity is 80%, and PPV is 90/110, or 82%; if prevalence halves, PPV falls even though sensitivity and specificity are unchanged.

Traps

  • A statistically significant result may not be clinically meaningful.
  • Confidence intervals crossing one for risk ratios or zero for mean differences mean no significant effect.
  • A small p-value does not measure effect size; report it with the estimate.