Coronary Arteries and their Supply to Cardiac Conduction System

The heart’s conduction system is responsible for regulating the heartbeat. The following are the coronary arteries that supply blood to the different parts of the cardiac conduction system:

Sinoatrial Node
The sinoatrial node, which is the primary pacemaker of the heart, is supplied by the right coronary artery in 60% of cases through a sinoatrial nodal branch.

Atrioventricular Node
The atrioventricular node, which is responsible for delaying the electrical impulse before it reaches the ventricles, is supplied by the right coronary artery in 80% of individuals through the atrioventricular nodal branch.

Atrioventricular Bundle
The atrioventricular bundle, which conducts the electrical impulse from the atria to the ventricles, is supplied by numerous septal arteries that mostly arise from the anterior interventricular artery, a branch of the left coronary artery.

Left Bundle Branch
The left bundle branch, which conducts the electrical impulse to the left ventricle, is supplied by numerous subendocardial bundle arteries that originate from the left coronary artery.

Right Bundle Branch
The right bundle branch, which conducts the electrical impulse to the right ventricle, is supplied by numerous subendocardial bundle arteries that originate from the right coronary artery.

ECG Changes and Localisation of Infarct in Coronary Artery Disease

Patients with chest pain and multiple risk factors for cardiac disease require prompt evaluation to determine the underlying cause. Electrocardiogram (ECG) changes can help localise the infarct to a particular territory, which can aid in diagnosis and treatment.

Inferior infarcts are often due to lesions in the right coronary artery, as evidenced by ST elevation in leads II, III, and aVF. However, in 20% of cases, this can also be caused by an occlusion of a dominant left circumflex artery.

Lateral infarcts involve branches of the left anterior descending (LAD) and left circumflex arteries, and are characterised by ST elevation in leads I, aVL, and V5-6. It is unusual for a lateral STEMI to occur in isolation, and it usually occurs as part of a larger territory infarction.

Anterior infarcts are caused by blockage of the LAD artery, and are characterised by ST elevation in leads V1-V6.

Blockage of the right marginal artery does not have a specific pattern of ECG changes associated with it, and it is not one of the major coronary vessels.

In summary, understanding the ECG changes associated with different coronary arteries can aid in localising the infarct and guiding appropriate treatment.

Different Cusps of Heart Valves

The heart has four valves that regulate blood flow through the chambers. Each valve is composed of cusps, which are flaps that open and close to allow blood to pass through. Here are the different cusps of each heart valve:

Aortic Valve: The aortic valve is made up of a right, left, and posterior cusp. It is located at the junction between the left ventricle and the ascending aorta.

Mitral Valve: The mitral valve is usually the only bicuspid valve and is composed of anterior and posterior cusps. It is located between the left atrium and the left ventricle.

Tricuspid Valve: The tricuspid valve has three cusps – anterior, posterior, and septal. It is located between the right atrium and the right ventricle.

Pulmonary Valve: The pulmonary valve is made up of right, left, and anterior cusps. It is located at the junction between the right ventricle and the pulmonary artery.

Understanding the different cusps of heart valves is important in diagnosing and treating heart conditions.

Diagnostic Investigations for Cardiac Conditions

When a patient presents with signs and symptoms of a cardiac condition, various diagnostic investigations may be performed to determine the underlying cause. In the case of a patient with chest tightness, the first-line investigation is usually an electrocardiogram (ECG) to rule out acute coronary syndrome. However, if the patient is suspected of having aortic stenosis (AS), the best diagnostic investigation is an echocardiogram and Doppler to measure the size of the aortic valve. A normal aortic valve area is more than 2 cm2, while severe AS is defined as less than 1 cm2.

Other diagnostic investigations for cardiac conditions include a coronary angiogram to assess the patency of the coronary arteries and potentially perform an angioplasty to insert a stent if any narrowing is found. Exercise tolerance tests can also be useful in monitoring patients with a cardiac history and heart failure classification. However, a D-dimer test, which is used to diagnose pulmonary embolism, would not be indicated in a patient with suspected AS unless there were additional features suggestive of a pulmonary embolism, such as calf tenderness.

Medications for Heart Failure: Understanding their Effects

Heart failure is a complex condition that requires careful management, including the use of various medications. In this context, it is important to understand the effects of each drug and how they can impact the patient’s health. Here is a brief overview of some commonly used medications for heart failure and their effects:

Diltiazem: This calcium-channel blocker can be used to treat angina and hypertension. However, it is advisable to stop calcium-channel blockers in patients with heart disease, as they can reduce the contractility of the heart, exacerbating the condition.

Spironolactone: This drug can help alleviate leg swelling by reducing water retention. It is also one of the three drugs in heart failure that have been shown to reduce mortality, along with ACE inhibitors and b-blockers.

Allopurinol: This medication is used in the prevention of gout long term and has no detrimental effect on the heart.

Paracetamol: This drug does not have an effect on the heart.

Lisinopril: This ACE inhibitor is used in the treatment of hypertension and the prophylactic treatment of angina. Stopping this medication is likely to worsen heart failure. Like spironolactone and b-blockers, ACE inhibitors have been shown to reduce mortality in heart failure, although the mechanisms behind this effect are not fully understood.

In summary, understanding the effects of medications for heart failure is crucial for optimizing patient care and improving outcomes. Healthcare providers should carefully consider each drug’s benefits and risks and tailor treatment to the individual patient’s needs.

Management of Heart Block in Acute Myocardial Infarction

Wenckebach’s phenomenon is usually not a cause for concern in patients with normal haemodynamics. However, if it occurs alongside acute myocardial infarction, complete heart block, or symptomatic Mobitz type II block, temporary pacing is necessary. Even with complete heart block, revascularisation can improve conduction if the patient is haemodynamically stable. Beta blockers should be avoided in second- and third-degree heart block as they can worsen the situation. Temporary pacing is required before proceeding to primary percutaneous intervention (PCI). A permanent pacemaker may be necessary for patients with irreversible heart block, but revascularisation should be prioritised as it may improve conduction. The block may be complete or second- or third-degree. If the heart block is reversible, temporary pacing should be followed by an assessment for permanent pacing.

For the management of heart failure, first line options include ACE inhibitors, beta-blockers, and aldosterone antagonists. In this case, the patient was already on a beta-blocker and an ACE inhibitor which had been effective. The addition of an aldosterone antagonist such as spironolactone would be the best option as it prevents fluid retention and reduces pressure on the heart. Ivabradine is a specialist intervention that should only be considered after trying all other recommended options. Addition of furosemide would only provide symptomatic relief. Insertion of an implantable cardiac defibrillator device is a late-stage intervention. Encouraging regular exercise and a healthy diet is important but does not directly address the patient’s clinical deterioration.

Treatment Options for Atrial Fibrillation in a Patient with Heart Failure

When treating a patient with atrial fibrillation (AF) and heart failure, the aim should be rate control. While bisoprolol is a good choice for medication, it may not be suitable for a patient with chronic low blood pressure. In this case, digoxin would be the treatment of choice. Anticoagulation with either a novel oral anticoagulant or warfarin is also necessary. Electrical cardioversion is not appropriate for this patient. Increasing the dose of bisoprolol may be reasonable, but considering the patient’s clinical presentation and past medical history, it may not be the best option. Amlodipine will not have an effect on rate control in AF, and calcium-channel blockers should not be used in heart failure. Amiodarone should not be first-line treatment in this patient due to her heart failure. Overall, the best treatment option for AF in a patient with heart failure should be carefully considered based on the individual’s medical history and current condition.

Coronary Artery Branches and Their Functions

The heart is supplied with blood by the coronary arteries, which branch off the aorta. These arteries are responsible for delivering oxygen and nutrients to the heart muscle. Here are some of the main branches of the coronary arteries and their functions:

1. Left Anterior Descending Artery: This artery supplies the front and left side of the heart, including the interventricular septum. It is one of the most important arteries in the heart.

2. Acute Marginal Branch of the Right Coronary Artery: This branch supplies the right ventricle of the heart.

3. Circumflex Branch of the Left Coronary Artery: This artery supplies the left atrium, left ventricle, and the sinoatrial node in some people.

4. Obtuse Marginal Branch of the Circumflex Artery: This branch supplies the left ventricle.

5. Atrioventricular Nodal Branch of the Right Coronary Artery: This branch supplies the atrioventricular node. Blockage of this branch can result in heart block.

Understanding the functions of these coronary artery branches is crucial for diagnosing and treating heart conditions.

Causes of Pulseless Electrical Activity

Pulseless Electrical Activity (PEA) occurs when there is a lack of pulse despite normal electrical activity on the ECG. This can be caused by poor intrinsic myocardial contractility or a variety of remediable factors. These factors include hypoxemia, hypovolemia, severe acidosis, tension pneumothorax, pericardial tamponade, hyperkalemia, hypocalcemia, poisoning with a calcium channel blocker, or hypothermia. Additionally, PEA may be caused by a massive pulmonary embolism. It is important to identify and address the underlying cause of PEA in order to improve patient outcomes.