Wellens' syndrome is an electrocardiographic manifestation of critical proximal left anterior descending (LAD) coronary artery stenosis in patients with unstable angina. It is characterized by symmetrical, often deep (>2 mm), T wave inversions in the anterior precordial leads. A less common variant is biphasic T wave inversions in the same leads.

First described by Hein J. J. Wellens and colleagues in 1982 in a subgroup of patients with unstable angina, it does not seem to be rare, appearing in 18% of patients in his original study. A subsequent prospective study identified this syndrome in 14% of patients at presentation and 60% of patients within the first 24 hours.

The presence of Wellens' syndrome carries significant diagnostic and prognostic value. All patients in the De Zwann's study with characteristic findings had more than 50% stenosis of the left anterior descending artery (mean = 85% stenosis) with complete or near-complete occlusion in 59%. In the original Wellens' study group, 75% of those with the typical syndrome manifestations had an anterior myocardial infarction. Sensitivity and specificity for significant (more or equal to 70%) stenosis of the LAD artery was found to be 69% and 89%, respectively, with a positive predictive value of 86%.

Wellens' sign has also been seen as a rare presentation of Takotsubo cardiomyopathy or stress cardiomyopathy.

Despite the grave initial presentation in some of the patients, most of the patients survive the initial acute event, with a very low rate of in-hospital mortality or complications. Once a patient has recovered from the acute stage of the syndrome, they can expect a favorable outcome and the long-term prognosis is excellent. Even when ventricular systolic function is heavily compromised at presentation, it typically improves within the first few days and normalises within the first few months. Although infrequent, recurrence of the syndrome has been reported and seems to be associated with the nature of the trigger.

Takotsubo cardiomyopathy is rare, affecting between 1.2% and 2.2% of people in Japan and 2% to 3% in western countries who suffer a myocardial infarction. It also affects far more women than men with 90% of cases being women, most postmenopausal. Scientists believe one reason is that estrogen causes the release of catecholamine and glucocorticoid in response to mental stress. It is not likely for the same recovered patient to experience the syndrome twice, although it has happened in rare cases. The average ages at onset are between 58 and 75 years. Less than 3% of cases occurred in patients under age 50.

Knowledge that TdP may occur in patients taking certain prescription drugs has been both a major liability and reason for retirement of these medications from the marketplace. Examples of compounds linked to clinical observations of TdP include amiodarone, fluoroquinolones, methadone, lithium, chloroquine, erythromycin, amphetamine, ephedrine, pseudoephedrine, methylphenidate, and phenothiazines. It has also been shown as a side effect of certain anti-arrhythmic medications, such as sotalol, procainamide, and quinidine. The gastrokinetic drug cisapride (Propulsid) was withdrawn from the US market in 2000 after it was linked to deaths caused by long QT syndrome-induced torsades de pointes. In many cases, this effect can be directly linked to QT prolongation mediated predominantly by inhibition of the hERG channel.

In September 2011 (subsequently updated in March 2012 and February 2013), the FDA issued a warning concerning increased incidence of QT prolongation in patients prescribed doses of the antidepressant Celexa (citalopram) above 40 mg per day, considered the maximum allowable dosage, thereby increasing the risk of Torsades. However, a study, "Evaluation of the FDA Warning Against Prescribing Citalopram at Doses Exceeding 40 mg," reported no increased risk of abnormal arrhythmias, thus questioning the validity of the FDA's warning.

In medicine, pulsus bisferiens, also bisferious pulse or biphasic pulse, is a sign where, on palpation of the pulse, a double peak per cardiac cycle can be appreciated. "Bisferious" means striking twice. Classically, it is detected when aortic insufficiency exists in association with aortic stenosis, but may also be found in isolated but severe aortic insufficiency, and hypertrophic obstructive cardiomyopathy.

Normally, arterial pulses are best felt in radial arteries but character is better assessed in carotid artery. Pulsus bisferiens is best felt in brachial and femoral arteries. Another pulse which can be confused with bisferiens is pulsus alternans which is felt better in peripheral arteries. The first lift is due to "percussion wave"(P) and the second lift is due to tidal wave (T).

- If P>T - AR>AS

- If T>P - AS>AR

Characteristic causes:

1. Aortic regurgitation (AR)

2. Aortic regurgitation with Aortic Stenosis (AR+AS)

3. Hypertrophic cardiomyopathy

The following is a list of factors associated with an increased tendency towards developing torsades de pointes:

- Hypokalemia (low blood potassium)

- Hypomagnesemia (low blood magnesium)

- Hypocalcemia (low blood calcium)

- Bradycardia (slow heartbeat)

- Heart failure

- Left ventricular hypertrophy

- Hypothermia

- Subarachnoid hemorrhage

- Hypothyroidism

The prevalence of ARVD is about 1/10,000 in the general population in the United States, although some studies have suggested that it may be as common as 1/1,000. Recently, 1/200 were found to be carriers of mutations that predispose to ARVC. Based on these findings and other evidence, it is thought that in most patients, additional factors such as other genes, athletic lifestyle, exposure to certain viruses, etc. may be required for a patient to eventually develop signs and symptoms of ARVC. It accounts for up to 17% of all sudden cardiac deaths in the young. In Italy, the prevalence is 40/10,000, making it the most common cause of sudden cardiac death in the young population.

The deletion that causes this disease can remove up to six different genes. These include:

- The uncharacterised protein C17orf69 (also known as FLJ25168).

- Corticotropin releasing hormone receptor 1 (CRHR1, also known as CRF-R, CRF1)

- Microtubule-associated protein tau (MAPT)

- The uncharacterised protein KIAA1267 (also known as DKFZP727C091)

17q21.31 microdeletion syndrome (Koolen De Vries syndrome) is a rare genetic disorder caused by a deletion of a segment of chromosome 17 which contains six genes. This deletion syndrome was discovered independently in 2006 by three different research groups.

Ventricular inversion, also known as atrioventricular discordance, is a condition in which the anatomic right ventricle of the heart is on the left side of the interventricular septum and the anatomic left ventricle is on the right.

Common causes include:

- Pulmonary hypertension

- Tetralogy of Fallot

- Pulmonary valve stenosis

- Pulmonic regurgitation

- Ventricular septal defect (VSD)

- High altitude

- Cardiac fibrosis

- Chronic obstructive pulmonary disease (COPD)

- Athletic heart syndrome

Arrhythmogenic right ventricular dysplasia (ARVD) is an inherited heart disease.

ARVD is caused by genetic defects of the parts of heart muscle (also called "myocardium" or "cardiac muscle") known as desmosomes, areas on the surface of heart muscle cells which link the cells together. The desmosomes are composed of several proteins, and many of those proteins can have harmful mutations.

The disease is a type of nonischemic cardiomyopathy that involves primarily the right ventricle. It is characterized by hypokinetic areas involving the free wall of the right ventricle, with fibrofatty replacement of the right ventricular myocardium, with associated arrhythmias originating in the right ventricle.

ARVD can be found in association with diffuse palmoplantar keratoderma, and woolly hair, in an autosomal recessive condition called Naxos disease, because this genetic abnormality can also affect the integrity of the superficial layers of the skin most exposed to pressure stress.

ARVC/D is an important cause of ventricular arrhythmias in children and young adults. It is seen predominantly in males, and 30–50% of cases have a familial distribution.

The pathophysiology of unstable angina is controversial. Until recently, unstable angina was assumed to be angina pectoris caused by disruption of an atherosclerotic plaque with partial thrombosis and possibly embolization or vasospasm leading to myocardial ischemia. However, sensitive troponin assays reveal rise of cardiac troponin in the bloodstream with episodes of even mild myocardial ischemia. Since unstable angina is assumed to occur in the setting of acute myocardial ischemia without troponin release, the concept of unstable angina is being questioned with some calling for retiring the term altogether.

Unstable angina (UA) is a type of angina pectoris that is irregular. It is also classified as a type of acute coronary syndrome (ACS).

It can be difficult to distinguish unstable angina from non-ST elevation (non-Q wave) myocardial infarction (NSTEMI). They differ primarily in whether the ischemia is severe enough to cause sufficient damage to the heart's muscular cells to release detectable quantities of a marker of injury (typically troponin T or troponin I). Unstable angina is considered to be present in patients with ischemic symptoms suggestive of an ACS and no elevation in troponin, with or without ECG changes indicative of ischemia (e.g., ST segment depression or transient elevation or new T wave inversion). Since an elevation in troponin may not be detectable for up to 12 hours after presentation, UA and NSTEMI are frequently indistinguishable at initial evaluation.

Smoking is the number one cause of Reinke's edema. Other factors include gastroesophageal reflux, hypothyroidism and chronic overuse of the voice. Smoking is the only risk factor that may lead to cancer. Additionally, the combination of several risk factors increase the likelihood of an individual developing Reinke's edema. For example, an individual who smokes and also has gastric reflux would have an increased susceptibility for developing Reinke's edema over time.

Reinke's edema is commonly diagnosed in middle-aged females with a history of smoking (aged 50 years or older). Because males have lower pitched voices than females, males are less likely to observe a significant changes in the voice, and are therefore less likely to seek treatment. Females also report more physical discomfort due to Reinke's edema. The risk of Reinke's edema increases with age and also with prolonged exposure to smoking. Additionally, individuals in professions that require constant use of the voice, such as singers, teachers, and radio hosts, may be at an increased risk for developing the disease.

Because the disease is heavily linked to smoking, there is no established way to screen for Reinke's edema. Similarly, the only way to prevent Reinke's edema is to avoid smoking. By adopting a non-smoking lifestyle after being diagnosed with Reinke's edema, it is possible to stop the disease's progression, although it is not possible to reverse it. Therefore, it is critical to maintain a non-smoking lifestyle even after surgery, because the fluid can re-emerge. In fact, in many cases surgeons will not perform surgery without the guarantee that the individual will stop smoking.

Sinus tachycardia is usually a response to normal physiological situations, such as exercise and an increased sympathetic tone with increased catecholamine release—stress, fright, flight, anger. Other causes include:

- Pain

- Fever

- Anxiety

- Dehydration

- Malignant hyperthermia

- Hypovolemia with hypotension and shock

- Anemia

- Heart failure

- Hyperthyroidism

- Mercury poisoning

- Kawasaki disease

- Pheochromocytoma

- Sepsis

- Pulmonary embolism

- Acute coronary ischemia and myocardial infarction

- Chronic obstructive pulmonary disease

- Hypoxia

- Intake of stimulants such as caffeine, theophylline, nicotine, cocaine, or amphetamines

- Hyperdynamic circulation

- Electric shock

- Drug withdrawal

- Porphyria

- Acute inflammatory demyelinating polyradiculoneuropathy

- Postural orthostatic tachycardia syndrome

While the exact incidence is unknown, estimates range from 33 - 57 percent of patients staying in the ICU for longer than 7 days. More exact data is difficult to obtain, since variation exists in defining the condition.

The three main risk factors for CIP and CIM are sepsis and systemic inflammatory response syndrome (SIRS), and multi-organ failure. Reported rates of CIP/CIM in people with sepsis and SIRS range from 68 to 100 percent. Additional risk factors for developing CIP/CIM include: female gender, high blood sugar (hyperglycemia), low serum albumin, and immobility. A greater severity of illness increases the risk of CIP/CIM. Such risk factors include: multi-organ dysfunction, renal failure, renal replacement therapy, duration of organ dysfunction, duration of ICU stay, low albumin, and central neurologic failure.

Certain medications are associated with CIP/CIM, such as corticosteroids, neuromuscular blocking agents, vasopressors, catecholamines, and intravenous nutrition (parenteral nutrition). Research has produced inconsistent results for the impact of hypoxia, hypotension, hyperpyrexia, and increased age on the risk of CIP/CIM. The use of aminoglycosides is "not" an independent risk for the development of CIP/CIM.

Among the causes of LBBB are:

- Aortic stenosis

- Dilated cardiomyopathy

- Acute myocardial infarction

- Extensive coronary artery disease

- Primary disease of the cardiac electrical conduction system

- Long standing hypertension leading to aortic root dilatation and subsequent aortic regurgitation

- Lyme disease

- Side effect of some cardiac surgeries (e.g., aortic root reconstruction)

A compartment syndrome is an increased pressure within a muscular compartment that compromises the circulation to the muscles.

Trisomy 8 mosaicism affects wide areas of chromosome 8 containing many genes, and can thus be associated with a range of symptoms.

- Mosaic trisomy 8 has been reported in rare cases of Rothmund-Thomson syndrome, a genetic disorder associated with the DNA helicase RECQL4 on chromosome 8q24.3. The syndrome is "characterized by skin atrophy, telangiectasia, hyper- and hypopigmentation, congenital skeletal abnormalities, short stature, premature aging, and increased risk of malignant disease".

- Some individuals trisomic for chromosome 8 were deficient in production of coagulation factor VII due to a factor 7 regulation gene (F7R) mapped to 8p23.3-p23.1.

- Trisomy and other rearrangements of chromosome 8 have also been found in tricho–rhino–phalangeal syndrome.

- Small regions of chromosome 8 trisomy and monosomy are also created by recombinant chromosome 8 syndrome (San Luis Valley syndrome), causing anomalies associated with tetralogy of Fallot, which results from recombination between a typical chromosome 8 and one carrying a parental paracentric inversion.

- Trisomy is also found in some cases of chronic myeloid leukaemia, potentially as a result of karyotypic instability caused by the fusion gene.

A compartment space is anatomically determined by an unyielding fascial (and osseous) enclosure of the muscles. The anterior compartment syndrome of the lower leg (often referred to simply as anterior compartment syndrome), can affect any and all four muscles of that compartment: tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius.

This term is often mistakenly used to describe various related/proximal conditions, including Anterior Shin Splints. It is important to distinguish between the two, as shin splints rarely causes serious health problems, while Anterior Compartment Syndrome can lead to irreversible damage.

The true compartment syndrome arises due to increased pressure within the unyielding anterior compartment of the leg. The pressure obstructs venous outflow, which causes further swelling and increased pressure. The resultant ischemia leads to necrosis (death of tissue) of the muscles and nerves. The process can begin with swelling of the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and/or the peroneus tertius muscles in response to strong eccentric contractions sufficient to produce postexercise soreness.

Left bundle branch block (LBBB) is a cardiac conduction abnormality seen on the electrocardiogram (ECG). In this condition, activation of the left ventricle of the heart is delayed, which causes the left ventricle to contract later than the right ventricle.

Wolff–Parkinson–White syndrome (WPW) is a disorder due to a specific type of problem with the electrical system of the heart which has resulted in symptoms. About 40% of people with the electrical problem never develop symptoms. Symptoms can include an abnormally fast heartbeat, palpitations, shortness of breath, lightheadedness, or syncope. Rarely cardiac arrest may occur. The most common type of irregular heartbeat that occurs is known as paroxysmal supraventricular tachycardia.

The cause of WPW is typically unknown. A small number of cases are due to a mutation of the PRKAG2 gene which may be inherited from a person's parents in an autosomal dominant fashion. The underlying mechanism involves an accessory electrical conduction pathway between the atria and the ventricles. It is associated with other conditions such as Ebstein anomaly and hypokalemic periodic paralysis. Diagnosis is typically when an electrocardiogram (ECG) show a short PR interval and a delta wave. It is a type of pre-excitation syndromes.

WPW syndrome is treated with either medications or radiofrequency catheter ablation. It affects between 0.1 and 0.3% in the population. The risk of death in those without symptoms is about 0.5% per year in children and 0.1% per year in adults. In those without symptoms ongoing observation may be reasonable. In those with WPW complicated by atrial fibrillation, cardioversion or the medication procainamide may be used. The condition is named after Louis Wolff, John Parkinson, and Paul Dudley White who described the ECG findings in 1930.

The definitive treatment of WPW is the destruction of the abnormal electrical pathway by radiofrequency catheter ablation. This procedure is performed by cardiac electrophysiologists. Radiofrequency catheter ablation is not performed in all individuals with WPW because inherent risks are involved in the procedure. When performed by an experienced electrophysiologist, radiofrequency ablation has a high success rate. Findings from 1994 indicate success rates of as high as 95% in people treated with radiofrequency catheter ablation for WPW. If radiofrequency catheter ablation is successfully performed, the condition is generally considered cured. Recurrence rates are typically less than 5% after a successful ablation. The one caveat is that individuals with underlying Ebstein's anomaly may develop additional accessory pathways during progression of their disease.

Right ventricular hypertrophy (RVH) is a form of ventricular hypertrophy affecting the right ventricle.

Blood travels through the right ventricle to the lungs via the pulmonary arteries. If conditions occur which decrease pulmonary circulation, meaning blood does not flow well from the heart to the lungs, extra stress can be placed on the right ventricle. This can lead to right ventricular hypertrophy.

It can affect electrocardiography (ECG) findings. An ECG with right ventricular hypertrophy may or may not show a right axis deviation on the graph.