Cardiac Arrest

Patients having a cardiac arrest will present with abrupt and drastic symptoms before the disease becomes eminent. In a number of cases, patients would suddenly collapse unconscious and may gain consciousness after a few minutes, or may never regain consciousness at all. It is also observable that breathing can arbitrarily stop during the cardiac event. Pulses may become faint or may not be appreciable at all especially during shock. In some cases of cardiac arrest, a number of signs may herald its onset like chest pain, fainting, dizziness, fatigue, shortness of breath, palpitation, vomiting, and weakness.

The following diagnostic modalities and tests are done to patients suspected of having cardiac arrest:

• Electrocardiogram (ECG): This test uses electrodes that are attached on the chest and limbs to detect the electrical activity of the heart [8]. Characteristic ECG tracing can reveal that cardiac arrest has recently occurred.
• Cardiac enzymes: This type of blood test detects the enzymes that is leaked by the damaged heart. 
• Electrolytes: Important electrolytes that helps propagate cardiac impulses like potassium, sodium, calcium, and magnesium can be quantitatively measured in the serum.
• Drug test: The use of a drug assay from the serum can determine the possible agents that could have caused the arrhythmia and eventually cardiac arrest.
• Thyroid hormones: The high levels of thyroid hormones may induce cardiac arrhythmias. 
• Chest X-ray: This imaging technique will show the actual shape of the heart and determine the presence of heart failure.
• Echocardiogram: This imaging modality will elucidate the part of the heart involved in ischemia and demonstrate any valvular abnormalities.
• Coronary angiogram: Contrast dyes could be delivered through a cardiac catheter to show any functional blockage to the vessels of the heart. 

The following treatment modalities are used in patients who present with cardiac arrest:

• CPR: Witnesses of an attack must ensue CPR right away as soon as the event happens to increase the survival chance [9]. CPR is focused on the restoration of airways, breathing and circulation before the patient is brought to the emergency room.
• Defibrillation: This makes use of an electric shock that is directly delivered to the chest to reverse the fibrillation. 
• Anti-arrhythmic drugs: In the emergency room, patients are given anti-arrhythmics to control the arrhythmia that caused the arrest. The more common anti-arrhythmic drugs used during cardiac arrest include angiotensin converting enzyme (ACE) inhibitors, calcium channel blockers, and amiodarone. 
• Implantable cardioverter-defibrillator (ICD): As soon as the patient is stabilized, this battery operated implantable device may be installed to perpetually monitor the heart rhythm and automatically give out charged impulses to stabilize the heart rhythm when the need arises [10].
• Coronary angioplasty: This is the surgical repair of the clogged vessels to restore the free flow of blood towards the heart muscles. 
• Coronary bypass surgery: This makes use of vein to surgically bypass the clogged coronary artery and restore normal blood flow and circulation.
• Corrective surgery: This procedure is done to repair congenital defects that predisposes to arrhythmias
• Heart transplant: Patients with heart failure and have concurrently experienced cardiac arrest will greatly benefit from a heart transplantation surgery. 

The prognosis of cardiac arrest greatly depends on several signs during the CPR phase. Patients will have better outlook when they have an unsupported systolic pressure of 90 mmHg after the arrest. For those who became unconscious during the cardiac arrest, a spontaneous vascular circulation within less than 25 minutes offers a good chance of survival after the event. Patients who stay unconscious may have a good outlook if they show signs of neurological responsiveness upon stimulation [7].

The most common condition that leads to cardiac arrest are cardiac arrhythmias [1]. There are a number of cardiac conditions that may lead to life-threatening cardiac arrhythmias:

• Coronary artery disease: This refers to heart diseases characterized by the clogging of vessels due to cholesterol deposits. The most common cause of sudden cardiac arrest is coronary artery disease. 
• Myocardial infarction: This cardiac condition is considered a severe and acute coronary disease that may trigger ventricular fibrillation and cardiac arrest. 
• Cardiomyopathy: The progressive enlargement and thickening of the heart muscles may lead to abnormal cardiac function and abnormal electrical impulses generation.
• Congenital heart diseases: The innate abnormalities seen in congenital heart diseases can trigger a cardiac arrest as well as the scars left in the myocardium after its corrective surgery among adults. 
• Valvular heart diseases: The stenosis or the regurgitation seen in heart valves can advertently lead to chamber enlargements that increases the risk for an arrhythmia.
• Electrical disorders of the heart: This refers to primary heart conditions that may lead to abnormal heart rhythms like long QT syndrome and Brugada syndrome [2].

In the United States, cardiac arrests account for at least 350,000 deaths per year. The annual prevalence rate translates to 1 to 2 cases per 1000 adult population. More than half of the cases of cardiac arrest have an underlying diagnosed or undiagnosed coronary artery disease. Patient who survives a cardiac arrest event will have a higher chance of recurrence within the first 6 to 24 months from the initial attack. Internationally, mortalities associated with cardiac arrests number up to 7 million deaths per year [3].

Among the more than 300,000 cardiac arrest deaths in the United States, at least 40% of these occur unwitnessed. Mortality in cardiac arrest greatly depends on the competence of the by-stander to conduct an immediate cardiopulmonary resuscitation (CPR) to the victim, and the duration between the time of arrest and the conduction of the patient to the nearest hospital [4]. Deaths with cardiac arrest are seen to be higher among the black races compared to the white ones [5]. Men are more prone to cardiac arrest than women with prevalence ratio of 3:1. In the Framingham cardiac studies, the highest age incidence where cardiac arrest was observed were between the ages 45 to 54 years old [6].

The abnormal electrophysiologic mechanisms involved in the development of arrhythmias that lead to cardiac arrest are diverse and multifactorial. Alteration in normal physiology that may affect the normal electroconductivity of the heart impulses emanates from the subcellular, cellular, tissue, and organ level. In the subcellular level, abnormalities in the sodium, potassium, and calcium channels increase the likelihood of ventricular tachyarrhythmias and ventricular fibrillation. A sick sinus at the cardiac tissue level that causes asystole and bradyarrhythmias accounts for 20% to 30% of cardiac arrest deaths. Organic defects with hypertrophic cardiomyopathy and dilated cardiomyopathy are associated with high risk for sudden cardiac arrest.

The best way to prevent the occurrence of a cardiac arrest is to actively reduce its established risk factors. Patients with diagnosed cardiac diseases must abide religiously with their maintenance medications and visit their cardiologist regularly. A smoke free and a stress free lifestyle will prevent a number of cardiac events and would significantly lower the strain to the heart. A nutritious diet that is good for the heart should also be in place. An active lifestyle with regular cardio exercises will lower the likelihood of a sudden cardiac arrest.

Cardiac arrest is described to be the sudden and unexpected loss of cardiac function, consciousness, and breathing. Cardiac arrest usually ensues with an inciting electrical disturbance to the heart resulting in pump failure and the discontinuation of the blood flow in circulation. Cardiac arrest is considered a medical emergency, any delay in resuscitative efforts can result to sudden cardiac death and eventually the patient’s demise.

Definition

Cardiac arrest is a medical term that refers to the mechanical cessation of the heart resulting to the absence of circulating blood in the system resulting to a serious physiologic disturbance.

Cause

The great majority of cardiac arrest is caused by cardiac arrhythmias. There are a number of cardiac disorders that predisposes to arrhythmias like coronary artery disease, myocardial infarction, cardiomyopathy, and congenital heart diseases.

Symptoms

Patients in cardiac arrest will acutely be unconscious with eminent signs of shock. Dizziness, fainting, chest pain, and fatigue may sometimes herald the disease process.

Diagnosis

ECG is imperative in the face of a cardiac arrest. Ancillary tests like cardiac enzymes, electrolytes, echocardiography, chest X-ray, and coronary angiogram are also done when the patient is stabilized.

Treatment and follow-up

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