Term
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Definition
Sinus Tacycardia
- An accelerated sinus rate that is a physiological response eg. to fever, anxiety, pain, exercise, hyperthyroidism
- HR >100 bpm and rhythm is usually regular
- P waves are similar to sinus rhythm
- Occasionally an inappropriate resting sinus tachy occurs (often seen in young women without structural heart disease, underlying mechanism may be abnormality within the sinus node or its autonomic input, or hypersensitivity of the sinus node to autonomic input)
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Term
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Definition
Atrial Tachycardias
- Tachyarrhythmia generated by the atrial tissue
- 10% of SVTs
- Can occur at any age, but there is an increased likelihood if the atria are diseased (HTN, pulmonary disease, previous cardiac surgery)
- Causes: digoxin toxicity, IHD, cardiomyopathy, rheumatic heart disease and sick sinus syndrome
- Either focal automatic activity (mainly) or due to re-entrant mechanism. Can have multiple foci of automatic activity
- Multifocal atrial tachycardia: 3 or more P-waves, usually seen in elderly patients with pulmonary disease. HR is >100 bpm, and ECG findings typically include an irregular rhythm, which may look similar to AF
- Treatment involves correcting the underlying disease process. Magnesium and verapamil may be effective.
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Term
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Definition
AVNRT
- Most common type of narrow QRS
- A re-entrant circuit that lies in or close to the AV node
- Typically starts in the later teens/20s – causes= caffeine, alcohol, anxiety
- Narrow QRS tachycardia ~ 180 bpm with P waves often absent (hidden in the QRS, as atrial and ventricular depolarisation occur at the same time)
- Carotid sinus massage/iv adenosine blocks the AV node, breaking the re-entry circuit and terminating the tachycardia in most cases
- Recurrent troublesome AVRNT = ablation
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Term
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Definition
MOA: Within the SA node it inhibits the If ("funny") current (a mixed Na+–K+ inward current activated by hyperpolarization and modulated by the autonomic nervous system). Blocking this channel reduces cardiac pacemaker activity, selectively slowing HR and allowing more time for blood to flow to the myocardium - in contrast to beta-blockers & CCBs, which not only reduce HR, but also cardiac contractility.
Indicated: Used in combination with beta blockers in people with heart failure
CI: sick sinus syndrome, potent inhibitors of CYP3A4, including azole antifungals (such as ketoconazole), macrolide antibiotics, nefazodone and the antiretroviral drugs nelfinavir and ritonavir. Use with verapamil or diltiazem
SE: luminous phenomena, bradycardia, headaches, 1st-degree AV block, ventricular extrasystoles, dizziness, blurred vision |
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Term
| Activation of the renin-angiotensin system (RAAS) |
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Definition
- When renal blood flow is reduced, juxtaglomerular cells in the kidneys convert the prorenin into renin and secrete it directly into the circulation
- Plasma renin then carries out the conversion of angiotensinogen, released by the liver, to angiotensin I
- Angiotensin I is subsequently converted to angiotensin II by the enzyme ACE (found in the lungs) – causes vasoconstriction and stimulates secretion of aldosterone causing the kidneys to ↑ reabsorption of Na and H2O into the blood & excrete K+
- This ↑ the volume of extracellular fluid in the body, which also increases BP
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Term
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Definition
Resistance = 8 ųL / ∏r4
(8 x viscosity x length
over
pi x radius to power of 4) |
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Term
| Cyanosis develops when... |
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Definition
| ...the level of reduced haemoglobin is over 5 g/dL (e.g.. right-to-left shunt) |
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