My heart skip skips a beat


The pause is to allow the atria to fully empty into the ventricle.

Heartbeat on an ECG trace

P Interval (Ventricular Diastole)

  • Atria and ventricles are relaxed
  • blood is flowing into the atria from the veins. 
  • Atrial pressure increases above that of the ventricle, AV valves open allowing blood to flow into the ventricle

P Wave (Atrial Systole) P-Q

Signal transduction from SA to AV nodes. 

  • SA node fires 
  • Atria contract causing atrial systole 
  • which forces all blood into the ventricles
  • emptying the atria.

Q Interval (End of Ventricular Diastole)

Depolarisation of interventricular (IV) septum 

  • AV valves remain open - all remaining blood squeezed into the ventricles. 
  • impulse from the SA node reaches the AV node 
  • which spreads the signal throughout the walls of the ventricles via bundles of His and Purkinje fibres
  • R peak is the end of ventricular diastole and the start of systole.

R Interval (Ventricular Systole)

Ventricular contraction

  • All blood is now within the ventricles
  • so pressure is higher than in the atria - AV valves close
  • ventricles start to contract although pressure is not yet high enough to open the SL (semilunar) valves

ST Segment (Ventricular Systole)

Ventricular contraction

  • Pressure increases until it equals Aortic pressure,
  • SL valves open
  • blood is ejected into the Aorta (and pulmonary artery) as ventricles contract
  • At this time the atria are in diastole and filling with blood returning from the veins.
  • plateau in ventricular arterial pressure

T Wave (Ventricular Diastole)

T= moment of Ventricular repolarisation immediately before ventricular relaxation

  • Ventricles relax
  • ventricular pressure is once again less than the aortic pressure 
  • so SL valves close
The Signs as Cardiac Rhythms
  • Aries: Normal Sinus Rhythm
  • Taurus: Ventricular fibrillation
  • Gemini: Ventricular tachycardia
  • Cancer: Atrial flutter
  • Leo: Torsades des Pointes
  • Virgo: Asystole
  • Libra: Junctional tachycardia
  • Scorpio: Wandering Atrial Pacemaker
  • Sagittarius: Sinus arrest
  • Capricorn: Bradycardia
  • Aquarius: 3rd degree AV block
  • Pisces: Atrial fibrillation


Cardiac anatomy today… I had a quick formative and found it straight forward which was great - just need to review cardio, joints and neuroanatomy. Happy studying!

“There are two main endocrine cell lines of the pancreas. The most prolific - the beta cells - are responsible for the secretion of insulin. Alpha cells secrete glucagon and these cell types are collectively known as islet cells. Acinar cells are exocrine in nature and synthesise and secrete digestive enzymes.”