Fractional Flow Reserve Measurements in the Management of Acute Coronary Artery Syndrome

Cardiovascular diseases are a leading cause of mortality and morbidity around the world. Coronary artery disease (CAD), commonly known as heart disease is the end product of atherosclerotic plaque formation. High blood pressure, smoking or high cholesterol levels are some of the risk factors that worsen the atherosclerotic condition. Stable angina and acute coronary artery syndrome (ACS) are the two main sub categories of clinical patterns produced by CAD. Coronary arteries that harden up due to the atherosclerosis limit the blood supply to the heart, thereby damaging the myocardial tissues (ischemia). Rupture of a vulnerable plaque causes occlusive intracoronary thrombus which further leads to the complete obstruction of blood supply, resulting in unstable angina or myocardial infarctions (heart attacks). Even though chest pain (angina) and discomfort are considered as the common symptoms of CAD, it is essential to perform the diagnostic procedures in order to distinguish patients with Acute Coronary artery syndrome. Prompt medical attention and diagnosis is crucial for treating the ACS patients as it is the major cause of infarctions.

Cardiac conditions with clinical patterns that represent myocardial infarctions and unstable angina fall into the category of ACS. Unstable angina, Non-ST-segment elevation myocardial infarction (NSTEMI) and ST-segment elevation myocardial infarction (STEMI) are the main classifications of ACS, diagnosed with the help of electrocardiograms (ECG) and blood tests. Devising a risk stratification method is possible only with in-vivo evaluation of the vulnerable plaque. Advanced medical imaging techniques such as intravascular ultrasound (IVUS), angioplasty surgery and optical coherence tomography (OCT) helps in assessing the pathophysiology of plaque formation, erosion and rupture. Treatment of acute coronary artery syndrome mainly involves medical therapy and revascularization procedures. Anti-ischemic agents, anti-platelet agents and anti coagulants are the standard pharmacological treatment options prescribed by physicians. Revascularization procedures include percutaneous coronary intervention (PCI) and Coronary Artery Bypass Graft (CABG). Fractional Flow Reserve guided percutaneous intervention helps the cardiologist determine whether to treat the lesions with stenting or medical therapy. The patient’s cardiac health, risk score and several other factors are taken into consideration to choose between and bypass and angioplasty surgery. 

Huge advancements have been made in evaluating the extent and severity of culprit lesions of ACS which helps in the effective management of the condition. Novel antiplatelet drugs, pressure wire guided percutaneous interventions, fractional flow reserve and drug eluting stent implantations are some of the noteworthy achievements. 

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Management of Atrial Fibrillation

The human heart is a muscular pump which beats as a result of electrical impulses produced by a special group of cells in the heart that have the ability to generate electrical activity on their own. Any abnormalities in the heart rate or rhythm can be considered to be a fault in the electrical conduction system of the heart. If the heart rate remains constantly slower (bradycardia) or faster (tachycardia) with irregular rhythm, then it may be a heart condition called arrhythmia. Diagnosis of arrhythmia involves collecting information about symptoms, evaluating medical history and a physical exam. Electrocardiogram, cardio monitoring and blood flow blood pressure measurements are some of the diagnostic tests, blood pressure and procedures performed to identify the underlying cause of abnormal heart rhythms.

Atrial fibrillation or A-fib (AF) is a type of arrhythmia that happens when the electrical signals are not only generated from sinus node, but are also generated from different places in and around the right atrium. When the atrioventricular node (AV node) – the electrical relay station between the upp and lower chambers of the heart-- is flooded with multiple erratic signals  it leads to twitching of atria and desynchronised contractions of heart chambers. There are mainly three types of atrial fibrillation - Paroxysmal Atrial Fibrillation, Persistent Atrial Fibrillation and Permanent Atrial Fibrillation. Whenever the A-fib lasts from a few seconds to about a week, it is termed as Paroxysmal Atrial Fibrillation and when the A-fib episode continues for more than seven days, the condition is called persistent atrial fibrillation. When the abnormal heart rhythm persists all the time, it is called permanent atrial fibrillation. Both the paroxysmal and persistent AF can progress to permanent AF over a period of time, which is why it is highly recommended to seek treatment as early as possible.  

AF episodes cause a disruption in the blood flow thereby increasing the likelihood of blood clot formation.  That is why risk of acute cardiovascular events and strokes are higher among people with atrial fibrillation. Treatment of Afib aims in cutting down the risk of blood clot formation and restoring the normal heart rhythm. Medical therapy using anticoagulants and electrical interventions are performed to treat this heart condition. Electro cardioversion, catheter ablation and surgical pocket maze are the standard procedures opted by the cardiologists to treat arrhythmias. In some cases, ablate and pace approach is recommended. During this procedure, the AV node is destroyed and an artificial pacemaker is placed in the surgical pocket of the chest to ensure a regular backup rhythm. Choosing between pharmacological treatment and ablation procedures always comes down to factors such as degree of AF episodes, cardio health and evaluation of surgical complications.

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Recent Advances in Cardiac Electrophysiology

Cardiology, being a prime medical speciality has always been in the forefront of inventing new diagnostic techniques, medical therapies, interventional procedures, medical imaging, continuous monitoring systems and more.  Among the many recent advancements, leadless pacemaker and thermocool smarttouch catheter offer a promising approach in treating problems with the heart's electrical conduction system.

Thermocool Smarttouch catheter: In a healthy heart, the electrical impulses are generated from the sinoatrial (SA) node which controls the speed or rhythm of beats. Any disruption or error in this conduction process leads to arrhythmia resulting in either too fast heart rate or too slow heart rate. Cardiac ablation is a medical procedure that is often preferred by the physicians to treat arrhythmias for those patients who don’t respond positively to drug therapy. During this catheterization procedure, continuous monitoring and radio frequency energy is used to scar the sources of abnormal heart rhythms. However, the procedure can fail sometimes because of inadequate lesion formation. Thermocool smarttouch catheter – an innovative discovery in electrophysiology focuses to resolve this drawback as it is integrated with contact-force sensing technology to provide detailed evaluation of catheter-to-myocardial contact force and catheter stability. This will guide the physicians to apply the stable force to the tissues without any risk of injury or complications.

Leadless pacemaker:Cardiologists have been recommending pacemakers for most of the patients suffering with bradyarrhythmias (too slow heart beat) or heart block. Taking over the job of the SA node, this electrical device restores electrical conduction through the heart. A surgical incision has to be made in the chest to place the pacemaker. Leads are connected to it which acts as a conduit for the delivery of electrical pulses that stimulate the heart functioning. However, acute and chronic complications arise whenever the surgical pocket is infected or leads are displaced. That is why leadless pacing technologies have gained immense interest in the field of cardiology. Self-contained leadless pacemakers that are different from its conventional counterparts don’t require any surgical incision or leads and can be placed through a catheterization procedure. Trial results and findings support the use of this less-invasive pacemaker technology.

It can be said that the future of interventional cardiology and electrophysiology looks bright and ensures to improve the quality of patient’s life.

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Use of Drug-Eluting Stents during Percutaneous Coronary Intervention

Narrowing of arteries and obstruction in the blood supply to the heart may lead to major cardiovascular events such as ischemia, myocardial infarction (heart attack), stroke and more. Plaques that build-up in the coronary arteries can behave in different ways: a plaque that grows to certain size and stops, a plaque that eventually causes blockage or a plaque that suddenly ruptures causing a complete block of blood supply. Chest pain during exertion is a sign of stable plaque whereas  heart attack or stroke occurs when there is a plaque rupture. Cardiologists will either opt for drug therapy or revascularization procedures - percutaneous coronary intervention and Coronary Artery bypass Grafting - depending on the diagnostic results of CAD patients.

Physicians often prefer a less invasive approach as it cuts down the complications and speeds up the recovery time. Percutaneous coronary intervention (PCI), also known as coronary angioplasty have become one of the most preferred coronary interventions because of its improved outcomes and dramatic reduction of major adverse cardiac events (MACE). The procedure mainly involves widening of the narrowed artery with an inflated balloon-tipped catheter thereby restoring the normal blood flow. However, in some cases it may be essential to perform a stenting procedure to keep the arteries open. An interventional cardiologist has to take the decision about whether or not to place the stents, based on angiographic data and fractional flow reserve measurements. Coronary Fractional Flow Reserve technique used during catheterization provides a lesion-specific index that guides the physician to decide the treatment approach. Stents are placed only when the measured FFR value is less than 0.75, otherwise the patient is prescribed with medical therapy.

The well-validated and threshold value provided by the coronary fractional flow reserve technique have become a standard and reliable way to demonstrate or exclude ischemia-inducing lesions. To return to the subject of stenting, two classes of stents namely Bare-metal stents (BMS) and Drug-Eluting Stents (DES) are available for PCI. DES has superseded the use of BMS as it prevents the formation of scar tissue thereby reducing the likelihood of restenosis to a greater extent. For instance, Cre8™ DES (a polymer-free DES coated with Amphilimus™) is a new step in DES technology that overcomes the polymer-associated complications and minimises the risk of thrombosis. The amphicilic carrier present in Cre8™ DES proposes a controlled and directed drug elution. Dramatic development of nanotechnology and DES technology offers a promising approach in developing a biocompatible stent that would completely eliminate restenosis and thrombosis in near future.

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Why Diagnosis of Treatment Resistant Hypertension is Important?

It is a well known fact that heart diseases have been claiming the lives of people more than any other disease. Termed as Coronary Heart Disease, this cardiac condition leads to heart attack, stroke and other major cardiovascular events. Treatment of coronary heart disease mainly focuses on controlling the risk factors by making lifestyle changes and prescribing drug treatments. High blood pressure (hypertension) and high blood cholesterol levels are the biggest risk factors that need to be brought under control. Several studies, clinical trials and research findings have stated that patients with resistant hypertension are even at higher risk of cardiovascular morbidity, stroke and mortality. Treatment resistant hypertension is a medical condition when the blood pressure remains stubbornly above the target in spite of the use of a diuretic and at least two other medications; patients whose blood pressure is controlled by four or more medications can be termed as resistant to treatment.

Accurate diagnosis and effective use of multiple drug regimens is significant in order to tackle treatment resistant hypertension. The goal blood pressure is less than 140/90 mmHg and achieving this level is even more important among resistant hypertension patients as it is associated with worse cardiovascular events. Taking accurate measurements of blood flow blood pressure is substantial for confirming treatment resistance. Direct (invasive) and indirect (non-invasive) methods are available for measuring the blood pressure and blood flow. Direct method involves using intra-arterial catheter to puncture a blood vessel and taking measurements directly, whereas the non-invasive method is about measuring the arterial pressure indirectly with a manual sphygmomanometer or an automated oscillometric device.

Physicians often prefer the indirect method because it’s the ‘gold standard’ method for routine measurements and monitoring. However, the accuracy levels of indirect measurements are low when compared to the direct methods. That is why it is important to have a hemodynamic monitoring system especially during the invasive procedures. Xper Flex Cardio physiomonitoring system introduced by Philips Healthcare is an innovative step towards this direction. It not only displays the invasive blood pressure blood flow, but also Fractional Flow Reserve measurements, ECG, respiration and other vital signs. Xper Flex Cardio systems prove to be of great use in areas where hemodynamic cardiac monitoring is required. To return to the subject of treatment resistant hypertension, we can say that ruling out the pseudoresistance factors and identification of the true causes can help in devising an effective prevention and management strategy of this condition.

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