Arrhythmias Quiz Part (1)

When a premature impulse is initiated, the tissue is in its absolute refractory period from the previous impulse. During this period, the tissue is unable to respond to any new stimulus and is temporarily unexcitable. As a result, the premature impulse cannot be conducted in either direction down either pathway. This refractory period allows the tissue to recover and reset its electrical properties before it can be stimulated again.

In the acute treatment of a symptomatic and/or hemodynamically unstable patient with sinus bradycardia, administering 0.5 mg of IV Atropine is recommended. Atropine is a medication that helps increase heart rate by blocking the action of the vagus nerve, which slows down the heart. By administering Atropine intravenously, it can quickly act on the body and increase the heart rate, improving symptoms and stabilizing the patient's condition.

Abnormal initiation of electrical impulses refers to the generation of electrical signals in the heart at irregular times or locations. This can lead to irregular heart rhythms or arrhythmias. Abnormal automaticity refers to the ability of certain cells in the heart to spontaneously generate electrical impulses, which can disrupt the normal electrical conduction system. Therefore, it is true that abnormal automaticity can result in abnormal initiation of electrical impulses.

The pacemaker of the heart is the SA node, also known as the sinoatrial node. This small group of cells located in the right atrium of the heart initiates electrical impulses that regulate the heart's rhythm and rate. These impulses then travel through the atria and ventricles, causing them to contract and pump blood. Therefore, the correct answer is False.

The SA node, also known as the sinoatrial node, is located in the right atrium of the heart and is responsible for initiating the electrical impulses that regulate the heart rhythm. It has the highest degree of automaticity among all the cardiac cells, meaning it has the ability to generate electrical impulses spontaneously without any external stimulation. This automaticity allows the SA node to set the pace for the rest of the heart, making it the natural pacemaker of the heart. Therefore, the statement "The SA node has the greatest degree of automaticity" is true.

During phase 2 of the cardiac action potential, the membrane potential is balanced by the exit of potassium ions from the cell. However, this exit is counteracted by the influx of calcium and sodium ions through slow calcium and slow sodium channels. This balanced movement of ions results in a plateau phase, which is a characteristic feature of phase 2. Therefore, the statement is true.

The statement is true because cardiac arrhythmias are indeed classified into two broad categories: supraventricular and ventricular. Supraventricular arrhythmias occur above the ventricles, which include the atria and the atrioventricular node. Ventricular arrhythmias, on the other hand, occur in the ventricles of the heart. This classification helps in understanding the location and origin of different types of arrhythmias, which in turn helps in determining the appropriate treatment strategies.

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During phase 3 of the cardiac action potential, the efflux (outward movement) of potassium ions is much higher than the influx (inward movement) of calcium and sodium ions. This leads to the repolarization of the ventricles, which is the process of restoring the electrical potential of the heart muscle cells back to their resting state after contraction. Therefore, the statement that the efflux of potassium ions greatly exceeds calcium and sodium influx during phase 3, resulting in the major component of ventricular repolarization, is true.

Myocardial ischemia refers to a condition where there is a lack of blood flow and oxygen supply to the heart muscle. This can result in various changes in the heart, including a decrease in the conduction velocity of electrical impulses. When the heart muscle is deprived of oxygen, it becomes less efficient in conducting electrical signals, leading to abnormalities in the heart's rhythm and potentially causing arrhythmias. Therefore, the statement that myocardial ischemia does not alter impulse conduction velocity is incorrect.

The explanation for the given correct answer is that for reentry to occur, there must be at least two pathways for the impulse to travel. This allows the impulse to continue circulating in a circuit, leading to a sustained abnormal rhythm. Additionally, there must be a "unidirectional block" in one of the conduction pathways, meaning that the impulse can only travel in one direction in that pathway. Finally, the velocity of impulse conduction must be slowed down in the other conduction pathway, further promoting the reentry circuit. These three conditions together create the necessary conditions for reentry to occur.

Transcutaneous pacing is a temporary method used to treat hemodynamically unstable sinus bradycardia. It involves the application of electrical impulses to the chest wall to stimulate the heart and increase the heart rate. Atropine is a medication commonly used to treat bradycardia, but if it is ineffective, transcutaneous pacing can be initiated as an alternative treatment option. Therefore, the statement is true.

The resting membrane potential of ventricular myocytes is typically between -70 to -90 mV. This means that the inside of the cell is more negatively charged compared to the outside. This electrical gradient is important for the normal functioning of the heart, as it allows for the generation and propagation of action potentials, which are essential for cardiac contraction and rhythm.

The statement is true because class I drugs are indeed subdivided into classes IA, IB, and IC. Class I drugs are a category of drugs that affect the action potential of cardiac cells and are used to treat certain heart conditions. The subdivision into classes IA, IB, and IC is based on their specific effects on cardiac cells and their mechanisms of action. This categorization helps in understanding the different properties and therapeutic uses of these drugs.

The statement is true because class IV drugs, such as diltiazem and verapamil, are indeed calcium channel blockers (CCBs). These medications work by blocking the calcium channels in the heart and blood vessels, leading to relaxation of the smooth muscles and dilation of the blood vessels. This helps to lower blood pressure and reduce the workload on the heart. Diltiazem and verapamil are commonly used to treat conditions such as high blood pressure, angina, and certain heart rhythm disorders.

Abnormal atrial automaticity can result in premature atrial contractions, atrial tachycardia, or atrial fibrillation. This is because abnormal automaticity refers to the generation of electrical impulses by the atrial tissue outside of the normal pacemaker cells. These abnormal impulses can disrupt the normal electrical activity of the atria, leading to irregular or rapid heart rhythms such as premature contractions, tachycardia, or fibrillation. Therefore, the statement that abnormal atrial automaticity will not result in these conditions is false.

If a patient is taking medication that is known to cause symptomatic sinus bradycardia, it is recommended to discontinue the medication whenever possible. This is because the medication could be the cause of the bradycardia. If the patient's heart rate remains slow even after stopping the medication and after a sufficient amount of time has passed (five half-lives of the drug), it is likely that the medication is not the cause of the bradycardia. Therefore, the statement "If the patient remains in sinus bradycardia after drug discontinuation and after five half-lives of the drug(s) have elapsed, then the drugs(s) can usually be excluded as the etiology of the arrhythmia" is true.

Class IC drugs are a type of antiarrhythmic medication that are known to have the greatest potency for slowing ventricular conduction. These drugs work by blocking sodium channels in the heart, which helps to slow down the electrical signals that control the heart's rhythm. By slowing ventricular conduction, these drugs can be effective in treating certain types of abnormal heart rhythms, such as ventricular tachycardia. Therefore, the statement that class IC drugs have the greatest potency for slowing ventricular conduction is true.

Cardiac arrhythmias can be caused by abnormal impulse initiation, meaning that the electrical signals that regulate the heartbeat are not generated properly. They can also be caused by abnormal impulse conduction, where the electrical signals are not transmitted correctly through the heart. Therefore, both of these factors can contribute to the development of cardiac arrhythmias.

A premature impulse refers to an electrical signal that occurs earlier than expected in the heart. In this case, the explanation states that if the impulse is only slightly premature and arrives after the tissue is no longer refractory, it can be conducted down both pathways. This means that the electrical signal can travel through both normal and abnormal pathways in the heart. Therefore, the statement is true.

When the membrane potential reaches the threshold, it triggers the opening of fast sodium channels. This allows sodium ions to flow into the cell rapidly. This influx of positive ions depolarizes the cell and generates an action potential, which is a rapid change in the membrane potential. Therefore, the statement is true.

Patients with hemodynamically unstable or severely symptomatic sinus bradycardia may require immediate intervention when atropine and temporary or transvenous pacing are not available. Isoproterenol, dopamine, and epinephrine are all potential treatment options in such cases. Isoproterenol is a beta-adrenergic agonist that increases heart rate and cardiac output. Dopamine is a catecholamine that can stimulate beta-1 adrenergic receptors and increase heart rate. Epinephrine is also a catecholamine with similar effects on heart rate and cardiac output. Therefore, all three options can be used as alternatives in the management of hemodynamically unstable or severely symptomatic sinus bradycardia.

Class III drugs are a category of antiarrhythmic medications that work by inhibiting ventricular repolarization and prolonging refractoriness. This means that they delay the time it takes for the heart's ventricles to reset after each heartbeat, which can help to prevent abnormal heart rhythms. Therefore, the statement that class III drugs inhibit ventricular repolarization and prolong refractoriness is true.

Atropine should be used cautiously in patients with myocardial ischemia or MI. This is because atropine can increase heart rate and worsen ischemia or MI by increasing the oxygen demand of the heart. Therefore, it is important to monitor these patients closely and use atropine with caution, if necessary.

This statement is true because class IA drugs have intermediate potency, meaning they have a moderate level of effectiveness or strength. On the other hand, class IB drugs have the lowest potency, indicating that they have the least amount of effectiveness or strength compared to other classes of drugs. Therefore, the statement accurately describes the potency levels of class IA and class IB drugs.

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During an action potential, the rapid influx of positive ions, particularly sodium ions, causes the depolarization of the ventricles. This depolarization is referred to as phase 0. As the positive ions enter the cell, the fast sodium channels responsible for their entry become inactivated. Therefore, the statement that the fast sodium channels become inactivated during phase 0 is true.

Amiodarone is classified as Class III antiarrhythmic drug. Class III drugs primarily work by blocking potassium channels, which prolongs the action potential duration and refractory period of cardiac cells. This helps to stabilize the rhythm of the heart and prevent abnormal heartbeats. Amiodarone is commonly used to treat various types of arrhythmias, including atrial fibrillation and ventricular tachycardia. It has a broad spectrum of action and can affect multiple ion channels, which is why it is classified as Class III.

They are (Beta) blockers not (Alpha)

efflux not influx

Class (I) drugs primarily decrease ventricular automaticity and slow down conduction velocity. These drugs are used to treat abnormal heart rhythms by suppressing the electrical activity in the heart. By reducing the automaticity and conduction velocity, Class (I) drugs help to stabilize the heart's rhythm and prevent arrhythmias. Therefore, the given statement that Class (I) drugs primarily increase ventricular automaticity and speed up conduction velocity is false.

Lidocaine and Mexiletin are classified as Class IB antiarrhythmic drugs. Class IB drugs primarily work by blocking sodium channels in the heart, which helps to decrease the excitability and conduction of electrical impulses. This class of drugs is particularly effective in treating ventricular arrhythmias, such as ventricular tachycardia and ventricular fibrillation. They have a fast onset of action and a short duration of effect. Class IB drugs have a moderate effect on the duration of the action potential and can help to stabilize the heart's electrical activity.

60 beats

repolarization not depolarization

sodium ions not calcium

Slow increase - Slow influx