Patterns Associated with Electrolyte Imbalances, Drug Toxicities and Physical and Chemical Agents

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© Springer Nature Singapore Pte Ltd. 2020
J. VarshneyElectrocardiography in Veterinary Medicinehttps://doi.org/10.1007/978-981-15-3699-1_9


9. ECG Patterns Associated with Electrolyte Imbalances, Drug Toxicities and Physical and Chemical Agents



J. P. Varshney1 


(1)
Veterinary Medicine, Shri Surat Panjarapole Prerit Nandini Veterinary Hospital, Surat, Gujarat, India

 



Intracellular concentration of K+ is approximately 30 times higher than the extracellular concentration in cardiac cells, while concentration of Na+ and Ca2+ is higher in extracellular fluid. Sodium and potassium pumps are active transport mechanisms responsible for resting membrane potential, depolarization, and repolarization of cardiac muscle cell. Hence appropriate concentrations of Na+, K+, and Ca2+ are important for normal depolarization and repolarization of cardiac cells. Any imbalance in the concentration of these electrolytes may lead to change in the pattern of electrocardiogram. Electrolyte imbalances are commonly seen in dehydration, severe vomiting, diarrheas, or renal failure. Electrocardiographic changes in response to electrolyte imbalances are detailed below.


9.1 ECG Changes Associated with Electrolyte Imbalance

























































































Electrolyte imbalances


Alterations in electrocardiogram


Hyperkalemia


– Large spiked “T” wave


– Short Q-T interval


– Flat or absence of “P” wave


– Wide “QRS”


– Depression of S-T segment


– Prolonged P-R interval


– Sinoventricular rhythm


– Slowing of heart rate


– Decrease in R amplitude


– Complete heart block in severe hyperkalemia


Hypokalemia


– Progressive S-T segment depression


– Small biphasic “T” wave


– Prolonged Q-T interval


– Appearance of U wave


– Tachyarrhythmia


– Delayed and abnormal repolarization


– Supraventricular and ventricular arrhythmias


– Increase in R amplitude


– Increased “P” wave amplitudes and durations (in severe hypokalemia)


Hypercalcemia


– Short Q-T interval. It may be fused with upstroke of “T” wave


Hypocalcemia


– Prolonged Q-T interval


– Tachyarrhythmia


– Q-T interval is correlated with plasma calcium levels


Hypermagnesemia


– Prolonged P-R interval


– Widening of QRS complexes


– Heart block


Hypomagnesemia


– Decreased resting membrane potential of myocardial cells


– Increased excitability of Purkinje fibers


– Wide QRS complexes


– S-T segment depression


– Peaked “T” wave


– Atrial fibrillation


– Supraventricular tachycardia


– Ventricular tachycardia


– Ventricular fibrillation


9.2 ECG Changes Associated with Drug Toxicities


A wide variety of drugs are used in the management of diseases in routine clinical practice in canine medicine. Many drugs are known to alter electrocardiographic pattern in dogs and cats, while many others may influence cardiovascular system owing to their potential side effects and may lead to changes in the electrocardiogram. The drugs, commonly employed in canine medicine, influencing cardiac functioning as side effects, are given below with their possible effects on electrocardiogram. Knowledge of such electrocardiographic alterations is important in routine management of clinical cases in dogs.
















































































































































































































































































Drugs


ECG changes


Amitriptyline


– Tachycardia


– Arrhythmias


– Conduction disturbances


Acetylpromazine


– Sinus bradycardia


Atropine


– Bradycardia followed by tachycardia is seen when atropine is given intravenously in doses higher than 0.015 mg/kg


– Atrial premature complexes (APCs), ventricular premature complexes (VPCs), second-degree AV block, or sinus tachycardia may be seen when atropine is given in doses less than 0.015 mg/kg intravenously


Amitraz


– Bradycardia


Amiodarone


– Arrhythmias


– Conduction disturbances


– Bradycardia or a systole


Atenolol


– Bradycardia


– Impaired atrioventricular conduction


Adrenaline


– Tachycardia


– Arrhythmia


Aminophylline


– Tachycardia


– Arrhythmia


Amphetamine


– Tachycardia


– Arrhythmia


Aminoglycosides


– Tachycardia


– Arrhythmias


Barbiturates


– Ventricular bigeminy


– Ventricular arrhythmias


Bretylium


– Ventricular tachycardia


Clindamycin and lincomycin (rapid IV in sensitive dogs)


– Cardiovascular collapse


Clomipramine


– Cardiac arrhythmias


– Tachycardia


Cimetidine


– Tachycardia (occasionally)


Calcium gluconate (rapid IV infusion)


– Bradycardia


– Shortening of Q-T interval


– S-T elevation


Cyclophosphamide


– Cardiac enlargement pattern


– Low-output heart failure


Digoxin


– Prolongation of P-R interval


– AV block (second or third degree)


– Sinus bradycardia or sinus arrest


– Ventricular premature complexes


– Accelerated junctional rhythm


– Ventricular tachycardia


– Paroxysmal atrial tachycardia with blocks


– Atrial fibrillation with slow ventricular rate


Doxorubicin


– Atrial premature complexes


– Ventricular tachycardia


– AV block


– Supraventricular arrhythmias


– Heart block


Diltiazem


– Prolong AV node conduction time


Diazepam


– Tachycardia


– Normal QRS


Ephedrine


– Tachycardia


Glycopyrrolate


– Increased heart rate


– Ventricular premature complexes (less frequent)


Halothane


– Sinus bradycardia


– Ventricular arrhythmias


Hydralazine


– Reflex tachycardia


– Hypotension


Isoproterenol


– Ectopic complexes


– Tachycardia


Isopropamide


– Tachycardia


Imipramine


– Sinus tachycardia


– AV bundle branch block


Lidocaine


– AV block


– Sinus arrest


– Pace maker suppression


– Asystole


Morphine


– Bradycardia


Nicotine


– Tachycardia


Norepinephrine


– Sinus tachycardia or atrial tachycardia


Neostigmine (ophthalmic)


– Bradycardia


Neostigmine methylsulfate


– Cardiac arrest


Organic phosphates


– Bradycardia or tachycardia


Oxyphenonium


– Bradycardia followed by tachycardia and arrhythmias


Prochlorperazine


– Tachycardia


Propantheline bromide


– Tachycardia


PGF2-alpha


– Tachycardia


– Ventricular tachycardia


Prazosin


– Hypotension


– Tachycardia (less frequent than with hydralazine)


Propranolol


– Pace maker suppression


– Atrioventricular (AV) block


Physostigmine (ophthalamic)


– Bradycardia


Quinidine


– Increased heart rate


– Q-T prolongation


– AV blocks


– Ventricular tachyarrhythmia


– Sinus arrest


– Wide QRS


– Pace maker suppression


– Asystole


– Ventricular fibrillation


– Heart block (first, second, and third degree)


Salbutamol


– Tachycardia


– Palpitation


Thiopental


– Cardiac arrest


Terbutaline


– Direct stimulation of SA node may cause sinus tachycardia


– Increased coronary circulation


– Enhanced myocardial perfusion


– Ventricular tachycardia


– Multifocal ventricular tachycardia


– Sinus tachycardia


– Atrioventricular (AV) block


Verapamil


– Pace maker suppression


– Atrioventricular block


Xylazine


– Sinus bradycardia


– Sinus arrest


– Sinoatrial block


– AV block


– Ventricular tachyarrhythmia

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Jul 17, 2021 | Posted by in INTERNAL MEDICINE | Comments Off on Patterns Associated with Electrolyte Imbalances, Drug Toxicities and Physical and Chemical Agents

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