The Student Physiologist – Online Cardiology Resource - -A guide to Cardiac Physiology- Send an email to [email protected] if you'd like to write for us, or want us to cover something specific. -TSP Mobile: ECG is now available on Google Play! The iOS version is incoming, but it takes a little longer to be added to the App Store. I'll update these sentences as soon as it's live.…

  • https://thephysiologist.org/study-materials/ ECG – The Student Physiologist - These pages will detail various aspects of ECG, the learning of which is vital during the PTP programme. I shall update them as my own studies progress and I'll add work from previous study as time allows. They will form an end product comprised of my lecture notes and outside research and, as a result, will be the basis of my revision material…
  • https://thephysiologist.org/study-materials/the-cardiac-cycle-and-cardiac-output/ The Cardiac Cycle And Cardiac Output – The Student Physiologist - Terms used throughout this page: LV- Left Ventricle ♦ (LV)EDV- (Left Ventricle) End Diastolic Volume ♦ ESV- End Systolic Volume ♦ MV- Mitral Valve ♦ AV- Aortic Valve ♦ PV- Pulmonary Valve ♦ TV- Tricuspid Valve ♦ SV- Stroke Volume The cardiovascular system's base job is to supply the required volume of blood to peripheral tissue…
  • https://thephysiologist.org/study-materials/cardiac-action-potentials/ Cardiac Action Potentials – The Student Physiologist - Cardiac action potentials differ from the APs found in other areas of the body. Typical neural AP duration is around 1ms and those of skeletal muscle are roughly 2-5ms, whereas cardiac action potentials range from 200-400ms. Nervous and muscle cells (as well as non-pacemaker cardiac cells) use the opening of Na channels to facilitate the depolarisation phase, whereas cardiac pacemaker cells use Ca ions…
  • https://thephysiologist.org/study-materials/the-ecg-leads-polarity-and-einthovens-triangle/ The ECG Leads, Polarity and Einthoven’s Triangle – The Student Physiologist - There are three lead systems that make up the standard ECG: Standard Limb Leads (Bipolar): I, IlI & III Augmented Limb Leads (Unipolar): aVR, aVL & aVF Precordial Leads: V1- V6 The Standard Limb Leads are used to display a graph of the potential difference recorded between two limbs at a time, ergo, they are bipolar. In these…
  • https://thephysiologist.org/study-materials/determining-cardiac-axis/ Determining Cardiac Axis – The Student Physiologist - The cardiac axis refers to the general direction in which the heart depolarises. Each wave of depolarisation begins at the Sinoatrial node, then spreads to the Atrioventricular node, before travelling to the Bundle of HIS and the Purkinje fibres to complete an electrical cardiac cycle. When viewing the heart from the front, imagine a clock…
  • https://thephysiologist.org/study-materials/electrodes-and-interference/ Electrodes And Skin Prep – The Student Physiologist - Biopotentials are voltages produced by tissues, particularly muscle tissue, during contraction. In a bit more detail, the concentration of K+ ions is much higher inside the cell compared to the extracellular environment (30-50x) and the Na+ ion concentration is 10x higher on the outside than the intracellular environment. When the membrane is stimulated to about 20mV an action potential…
  • https://thephysiologist.org/study-materials/the-normal-ecg/ The Normal ECG – The Student Physiologist - Standard Calibration A standard ECG is recorded at 25mm/sec and with a frequency cut off of no lower than 150Hz in adults, and 250Hz in children. On the standard ECG paper, with standard calibration, the squares represent:  The standard calibration signal will look like this: This will be present at the beginning or end of all four rows of…
  • https://thephysiologist.org/study-materials/the-sinus-rhythms/ The Sinus Rhythms – The Student Physiologist - Sinus Rhythm Normal rhythm and rate P Waves present- originating in SA node. Sinus Tachycardia Sinus Rhythm, >100bpm Expected with exercise Expected with fear/ pain Normal in children Can be caused by: Hypoxia Hypercarbia Pulmonary Embolism ß- Agonists Can occur without obvious stimuli. (More common in young females) Tachycardia at rest suggests a pathology Could represent…
  • https://thephysiologist.org/study-materials/atrial-flutter/ Atrial Flutter – The Student Physiologist - Atrial flutter is a supraventricular tachycardic arrhythmia that tends to occur in individuals of an advanced age, although  it is linked to endurance sports, also. In cases of atrial flutter, the normal conduction pathway of the heart from the Sinoatrial node, through the atrioventricular node to the ventricles, is interrupted causing a re-entry pathway. This pathway can be…
  • https://thephysiologist.org/study-materials/atrial-fibrillation/ Atrial Fibrillation – The Student Physiologist - Atrial fibrillation (AF) is the most common non-sinus tachycardia Typically, AF is caused by rapidly firing foci. Usually, the primary signal would emanate from the sinus node, and then spread across both atria in a controlled manner, before reaching the atrioventricular node, as normal. In the case of atrial fibrillation, the firing of disorganised impulses originating…
  • https://thephysiologist.org/study-materials/av-blocks/ AV Blocks – The Student Physiologist - The normal conduction pathway of the heart, (wherein depolarisation begins at the SA node and spreads to the AVN, HIS bundle and then through the bundle branches and Purkinje system) can become hindered or blocked.   These blocks should be, in theory at least, relatively obvious on the ECG trace, when one considers the properties of a normal trace; a…
  • https://thephysiologist.org/study-materials/avnrt-and-avrt/ AVNRT and AVRT – The Student Physiologist - Arrhythmias caused by a surplus conduction circuit between atrial and ventricular anatomy. They cause the normal electrical circuit to allow an impulse to repeatedly travel around the normal AV node and this new connection. AVNRT Atrioventricular Nodal Re-entrant Tachycardia The most common supraventricular arrhythmia in humans The most common cause of palpitations in patients with normal heart structure…
  • https://thephysiologist.org/study-materials/bundle-branch-blocks/ Bundle Branch Blocks – The Student Physiologist - The left and right bundle branches (LBB & RBB) are the areas of the cardiac conduction system responsible for carrying the depolarisation signal to the ventricles.   They allow for the rapid activation of both ventricles simultaneously. The are supplied with blood via the coronary arteries, predominantly; The left anterior descending coronary artery supplies the LBB, and…
  • https://thephysiologist.org/study-materials/ectopic-beats-palpitations/ Ectopic Beats & Palpitations – The Student Physiologist - Palpitations Palpitations are a reported symptom and a diagnosis, and describe  one's awareness of the myocardial contraction within the chest, with sensations such as: Pounding Quick beats Skipped beats They do not necessarily indicate an abnormality of the heart structure, but are often a symptom of an arrhythmia. Palpitation and its sensation result from the increased blood volume and forced…
  • https://thephysiologist.org/study-materials/ventricular-tachycardia/ Ventricular Tachycardia – The Student Physiologist -   Ventricular tachycardia exhibits 4 or more ventricular ectopic beats at a HR of 150-200bpm. It results from two possible mechanisms: A latent ventricular focus/ enhanced automaticity in a ventricular pacemaker   A re-entry circuit around a fixed anatomical area of the ventricular myocardium   There exist a number of variances in VT: Rate Morphology Duration Frequency Regularity VT…
  • https://thephysiologist.org/study-materials/hypertrophy/ Hypertrophy – The Student Physiologist - Hypertrophy is defined as the enlargement of an organ or tissue due to the increased size of its cells. Cardiac hypertrophy then, denotes the increased mass of the heart's constituent chamber walls. This enlargement is due to an overload, in response to which the chamber in question dilates so as to handle the increased volume of blood within it. An…
  • https://thephysiologist.org/study-materials/cardiomyopathies/ Cardiomyopathies – The Student Physiologist - Literally means heart (cardio) muscle (myo) disease (pathy) and describes a condition that impairs the heart's ability to expel blood efficiently, resulting in a reduced cardiac output and flow. There are three principal types; Dilated Cardiomyopathy (DCM) Hypertrophic Cardiomyopathy (HCM) Restrictive Cardiomyopathy (RCM) Mortality is increased, with a 2 year survival of 50% Dilated Cardiomyopathy Occurs as the result of a…
  • https://thephysiologist.org/study-materials/acute-coronary-syndromes/ Acute Coronary Syndromes – The Student Physiologist - Acute Coronary Syndrome  Myocardial ischaemia as a result of MI, either non-ST elevated, or ST elevated (NSTEMI or STEMI) or unstable angina Pathophysiology The atherosclerotic process within blood vessels creates a vulnerable plaque, which houses a necrosis containing 'tissue factor'. When the plaque becomes disrupted and tissue factor is exposed to the bloodstream, a coagulation cascade is…
  • https://thephysiologist.org/study-materials/myocardial-infarction/ Myocardial Infarction – The Student Physiologist - The heart needs an oxygenated blood supply in order to function in the same way as the rest of the body. The coronary arteries supply the surface of the heart muscle with this oxygenated blood, so when the lumen of one or more of these vessels becomes occluded, the required oxygen supply may not be sufficient…
  • https://thephysiologist.org/study-materials/q-waves/ Q Waves – The Student Physiologist - Q waves are the first deflection of the QRS complex, and are the representation of septal depolarisation within the heart. They are usually absent from most leads of the ECG, but small Q waves are normal in the leads that observe the heart from the left; I II aVL V5 V6 Q waves are sometimes seen…
  • https://thephysiologist.org/study-materials/cardiac-channelopathies/ Cardiac Channelopathies – The Student Physiologist - Blanket term for numerous conditions affecting the cardiac conduction system Conduction speed can be increased or decreased Ion channel mutations Major cause of sudden cardiac death 5-15% of patients have structurally normal hearts Inherited disorders that present with arrhythmia and multi-organ involvement Long QT Syndrome Brugada Polymorphic VT Short QT Syndrome Genes responsible include: KCNQ1…
  • https://thephysiologist.org/study-materials/brugada-syndrome/ Brugada Syndrome – The Student Physiologist -   A syndrome recognised as being a major cause of sudden cardiac death Patients have structurally normal hearts Autosomal dominant inheritance with cardiac sodium channel encoding gene SCN5A Predisposes patient to ventricular tachyarrhythmias  Prevalent in Southeast Asia, particularly in Japan and Thailand. Higher recorded incidence in males Genetic distribution is equal between genders Present in all age groups…
  • https://thephysiologist.org/study-materials/pulmonary-hypertension/ Pulmonary Hypertension – The Student Physiologist - An increase in mean pulmonary arterial pressure (PAP) ≥ 25mmHg at rest, as assessed by right heart catheterisation An increased blood pressure in the pulmonary arteries Denotes an increase in the pressure the heart must exert in order to pump blood through the pulmonary circulatory system to the lungs Below are the normal pulmonary and systemic pressures…
  • https://thephysiologist.org/study-materials/heart-failure/ Heart Failure – The Student Physiologist - The term "heart failure"(HF) describes an abnormality of the cardiac structure/function that leads to failure of the organ to deliver oxygen sufficient in rate to the metabolising tissues, despite normal filling pressures. It is actually a blanket term that covers a broad range of pathologies, but usually presents with specific signs and symptoms; Breathlessness Ankle swelling Fatigue…
  • https://thephysiologist.org/study-materials/ecg-artifact/ ECG Artifact – The Student Physiologist - Electrode Misplacement LA and RA electrodes are not interchangeable. Switching these leads will, if not corrected, produce the following deviations from the norm: Abnormal Inversion I A finding of Dextrocardia, but abnormal with proper R wave progression in Precordial leads Abnormal "normal" aVR RAD Reversing the leg electrodes, whilst not good practice, doesn't actually produce distinguishable…
  • https://thephysiologist.org/study-materials/ambulatory-ecg-monitoring/ Ambulatory ECG Monitoring – The Student Physiologist - Long term ECG recording is used to assess or monitor a patient's heart rhythm and conduction over and extended period of time. It is also employed to gauge the risk stratification of a population, and to monitor the efficacy of prognostic medical therapy on known rhythm abnormalities. There exist many different brands of ambulatory ECG (AmbECG) recorder,…
  • https://thephysiologist.org/study-materials/syncope/ Syncope – The Student Physiologist - Syncope is a transient loss of consciousness (T-LOC), due to global cerebral hypoperfusion (an inadequate supply of oxygen) characterised by rapid onset/offset short duration spontaneous complete recovery There are two reasons to evaluate patients presenting with syncope; To identify the precise cause in order to find an effective method of specific treatment of the mechanism of syncope To…
  • https://thephysiologist.org/study-materials/blood-pressure-and-measurement/ Blood Pressure And Measurement – The Student Physiologist - Blood flow always travels down a pressure gradient of high to low. The value for pressure difference is gained with: And the basic calculation for discerning resistance: (CO is Cardiac Output) Blood flow is given by: The distribution of systemic blood flow at rest Distribution is determined by Blood pressure Vascular resistance Vessel diameter largely…
  • https://thephysiologist.org/study-materials/vaughan-williams-classification/ Vaughan-Williams Classification – The Student Physiologist - ERP: Effective Refractory Potential APD: Action Potential Duration Anti-arrhythmic medications have a variety of different actions and mechanisms, and the Vaughan-Williams classification groups them accordingly. When this table was initially devised, there were far less anti-arrhythmic medications in comparison to the number available now and our understanding of pharmaceutical mechanisms is, although still incomplete, far…

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