There are a number of different biomarkers used to determine the presence of cardiac muscle damage. Troponins, measured through a blood test, are considered to be the best, and are preferred because they have greater sensitivity and specificity for measuring injury to the heart muscle than other tests. A rise in troponin occurs within 2–3 hours of injury to the heart muscle, and peaks within 1–2 days. The gross value of the troponin, as well as a change over time, are useful in measuring and diagnosing or excluding myocardial infarctions, and the diagnostic accuracy of troponin testing is improving over time. One high-sensitivity cardiac troponin is able to rule out a heart attack as long as the ECG is normal.

Other tests, such as CK-MB or myoglobin, are discouraged. CK-MB is not as specific as troponins for acute myocardial injury, and may be elevated with past cardiac surgery, inflammation or electrical cardioversion; it rises within 4–8 hours and returns to normal within 2–3 days. Copeptin may be useful to rule out MI rapidly when used along with troponin.

There are various risk assessment systems for determining the risk of coronary artery disease, with various emphasis on different variables above. A notable example is Framingham Score, used in the Framingham Heart Study. It is mainly based on age, gender, diabetes, total cholesterol, HDL cholesterol, tobacco smoking and systolic blood pressure.

Noninvasive imaging plays an important role in the diagnosis and characterisation of myocardial infarction. Tests such as chest X-rays can be used to explore and exclude alternate causes of a person's symptoms. Tests such as stress echocardiography and myocardial perfusion imaging can confirm a diagnosis when a person's history, physical examination (including cardiac examination) ECG, and cardiac biomarkers suggest the likelihood of a problem.

Echocardiography, an ultrasound scan of the heart, is able to visualize the heart, its size, shape, and any abnormal motion of the heart walls as they beat that may indicate a myocardial infarction. The flow of blood can be imaged, and contrast dyes may be given to improve image. Other scans using radioactive contrast include SPECT CT-scans using thallium, sestamibi (MIBI scans) or tetrofosmin; or a PET scan using Fludeoxyglucose or rubidium-82. These nuclear medicine scans can visualize the perfusion of heart muscle. SPECT may also be used to determine viability of tissue, and whether areas of ischemia are inducible.

Medical societies and professional guidelines recommend that the physician confirm a person is at high risk for myocardial infarction before conducting imaging tests to make a diagnosis, as such tests are unlikely to change management and result in increased costs. Patients who have a normal ECG and who are able to exercise, for example, do not merit routine imaging.

A stress test, is just that, a test to put stress on the heart through exercise. A doctor will put a patient through a series of exercises to measure the tolerance for stress on the heart. This test uses an ECG to detect the electrical impulses of the heart during physical exertion.

During this test a patient is put on a treadmill or a stationary bike. The incline or resistance of the bike are steadily increased until the patient reaches the target heart rate for the patient's age and weight.

An exercise stress test is not always accurate in determining if one has a blockage in the arteries. Women and those who are young may show abnormalities on their test even though no signs of coronary ischemia or CAD are present.

In "stable" angina, chest pain with typical features occurring at predictable levels of exertion, various forms of cardiac stress tests may be used to induce both symptoms and detect changes by way of electrocardiography (using an ECG), echocardiography (using ultrasound of the heart) or scintigraphy (using uptake of radionuclide by the heart muscle). If part of the heart seems to receive an insufficient blood supply, coronary angiography may be used to identify stenosis of the coronary arteries and suitability for angioplasty or bypass surgery.

Stable coronary artery disease (SCAD) is also often called stable ischemic heart disease (SIHD). A 2015 monograph explains that "Regardless of the nomenclature, stable angina is the chief manifestation of SIHD or SCAD." There are U.S. and European clinical practice guidelines for SIHD/SCAD.

A coronary angiography is performed only after a stress test or ECG shows a sign of coronary ischemia or CAD. This test is very important in finding where the blockages are in the arteries.

This test helps determine if an angioplasty or bypass surgery is needed.

During this test the doctor makes a small incision in the patient's groin (femoral) or wrist (radial) and inserts a catheter. The catheter has a very small video camera on the end of it so that the doctor can find the arteries.

Once he has found the arteries, he injects a dye in them so that he/she can detect any blockages in the arteries. The dye is able to be seen on a special x-ray machine.

The test takes one to two hours.

Prognosis in heart failure can be assessed in multiple ways including clinical prediction rules and cardiopulmonary exercise testing. Clinical prediction rules use a composite of clinical factors such as lab tests and blood pressure to estimate prognosis. Among several clinical prediction rules for prognosticating acute heart failure, the 'EFFECT rule' slightly outperformed other rules in stratifying patients and identifying those at low risk of death during hospitalization or within 30 days. Easy methods for identifying low-risk patients are:

- ADHERE Tree rule indicates that patients with blood urea nitrogen < 43 mg/dl and systolic blood pressure at least 115 mm Hg have less than 10% chance of inpatient death or complications.

- BWH rule indicates that patients with systolic blood pressure over 90 mm Hg, respiratory rate of 30 or fewer breaths per minute, serum sodium over 135 mmol/L, no new ST-T wave changes have less than 10% chance of inpatient death or complications.

A very important method for assessing prognosis in advanced heart failure patients is cardiopulmonary exercise testing (CPX testing). CPX testing is usually required prior to heart transplantation as an indicator of prognosis. Cardiopulmonary exercise testing involves measurement of exhaled oxygen and carbon dioxide during exercise. The peak oxygen consumption (VO2 max) is used as an indicator of prognosis. As a general rule, a VO2 max less than 12–14 cc/kg/min indicates a poor survival and suggests that the patient may be a candidate for a heart transplant. Patients with a VO2 max 35 from the CPX test. The heart failure survival score is a score calculated using a combination of clinical predictors and the VO2 max from the cardiopulmonary exercise test.

Heart failure is associated with significantly reduced physical and mental health, resulting in a markedly decreased quality of life. With the exception of heart failure caused by reversible conditions, the condition usually worsens with time. Although some people survive many years, progressive disease is associated with an overall annual mortality rate of 10%.

Approximately 18 of every 1000 persons will experience an ischemic stroke during the first year after diagnosis of HF. As the duration of follow-up increases, the stroke rate rises to nearly 50 strokes per 1000 cases of HF by 5 years.

Ischemic cardiomyopathy can be diagnosed via magnetic resonance imaging (MRI) protocol, imaging both global and regional function. Also the Look-Locker technique is used to identify diffuse fibrosis; it is therefore important to be able to determine the extent of the ischemic scar. Some argue that only left main- or proximal-left anterior descending artery disease is relevant to the diagnostic criteria for ischemic cardiomyopathy. Myocardial imaging usually demonstrates left ventricular dilation, severe ventricular dysfunction, and multiple infarctions. Signs include congestive heart failure, angina edema, weight gain and fainting, among others.

One of the most important features differentiating ischemic cardiomyopathy from the other forms of cardiomyopathy is the shortened, or worsened all-cause mortality in patients with ischemic cardiomyopathy. According to several studies, coronary artery bypass graft surgery has a survival advantage over medical therapy (for ischemic cardiomyopathy) across varied follow-ups.

Blood tests routinely performed include electrolytes (sodium, potassium), measures of kidney function, liver function tests, thyroid function tests, a complete blood count, and often C-reactive protein if infection is suspected. An elevated B-type natriuretic peptide (BNP) is a specific test indicative of heart failure. Additionally, BNP can be used to differentiate between causes of dyspnea due to heart failure from other causes of dyspnea. If myocardial infarction is suspected, various cardiac markers may be used.

According to a meta-analysis comparing BNP and N-terminal pro-BNP (NTproBNP) in the diagnosis of heart failure, BNP is a better indicator for heart failure and left ventricular systolic dysfunction. In groups of symptomatic patients, a diagnostic odds ratio of 27 for BNP compares with a sensitivity of 85% and specificity of 84% in detecting heart failure.

The survival of PVF largely depends on the promptness of defibrillation. The success rate of prompt defibrillation during monitoring is currently higher than 95%. It is estimated that the success rate decreases by 10% for each additional minute of delay.

After return of heart function, there has been a moderately higher risk of death in the hospital when compared to MI patients without PVF. Whether this still holds true with the recent changes in treatment strategies of earlier hospital admission and immediate angioplasty with thrombus removal is unknown. PVF does not affect the long-term prognosis.

Unstable angina is characterized by at least one of the following:

1. Occurs at rest or minimal exertion and usually lasts more than 20 minutes (if nitroglycerin is not administered)

2. Being severe (at least Canadian Cardiovascular Society Classification 3) and of new onset (i.e. within 1 month)

3. Occurs with a crescendo pattern (brought on by less activity, more severe, more prolonged or increased frequency than previously).

Fifty percent of people with unstable angina will have evidence of necrosis of the heart's muscular cells based on elevated cardiac serum markers such as creatine kinase isoenzyme (CK)-MB and troponin T or I, and thus have a diagnosis of non-ST elevation myocardial infarction.

A complication that may occur in the acute setting soon after a myocardial infarction or in the weeks following is cardiogenic shock. Cardiogenic shock is defined as a hemodynamic state in which the heart cannot produce enough of a cardiac output to supply an adequate amount of oxygenated blood to the tissues of the body.

While the data on performing interventions on individuals with cardiogenic shock is sparse, trial data suggests a long-term mortality benefit in undergoing revascularization if the individual is less than 75 years old and if the onset of the acute myocardial infarction is less than 36 hours and the onset of cardiogenic shock is less than 18 hours. If the patient with cardiogenic shock is not going to be revascularized, aggressive hemodynamic support is warranted, with insertion of an intra-aortic balloon pump if not contraindicated. If diagnostic coronary angiography does not reveal a culprit blockage that is the cause of the cardiogenic shock, the prognosis is poor.

Angina should be suspected in people presenting tight, dull, or heavy chest discomfort that is:

1. Retrosternal or left-sided, radiating to the left arm, neck, jaw, or back.

2. Associated with exertion or emotional stress and relieved within several minutes by rest.

3. Precipitated by cold weather or a meal.

Some people present with atypical symptoms, including breathlessness, nausea, or epigastric discomfort or burning. These atypical symptoms are particularly likely in older people, women, and those with diabetes.

Anginal pain is not usually sharp or stabbing or influenced by respiration. Antacids and simple analgesics do not usually relieve the pain. If chest discomfort (of whatever site) is precipitated by exertion, relieved by rest, and relieved by glyceryl trinitrate, the likelihood of angina is increased.

In angina patients momentarily not feeling any chest pain, an electrocardiogram (ECG) is typically normal unless there have been other cardiac problems in the past. During periods of pain, depression, or elevation of the ST segment may be observed. To elicit these changes, an exercise ECG test ("treadmill test") may be performed, during which the patient exercises to his/her maximum ability before fatigue, breathlessness, or pain intervenes; if characteristic ECG changes are documented (typically more than 1 mm of flat or downsloping ST depression), the test is considered diagnostic for angina. Even constant monitoring of the blood pressure and the pulse rate can lead to some conclusion regarding angina. The exercise test is also useful in looking for other markers of myocardial ischemia: blood pressure response (or lack thereof, in particular, a drop in systolic blood pressure), dysrhythmia and chronotropic response. Other alternatives to a standard exercise test include a thallium scintigram or sestamibi scintigram (in patients unable to exercise enough for the purposes of the treadmill tests, e.g., due to asthma or arthritis or in whom the ECG is too abnormal at rest) or Stress Echocardiography.

In patients in whom such noninvasive testing is diagnostic, a coronary angiogram is typically performed to identify the nature of the coronary lesion, and whether this would be a candidate for angioplasty, coronary artery bypass graft (CABG), treatment only with medication, or other treatments. In hospitalized patients with unstable angina (or the newer term of "high-risk acute coronary syndromes"), those with resting ischaemic ECG changes or those with raised cardiac enzymes such as troponin may undergo coronary angiography directly.

Hospital admission for people with the following symptoms is recommended, as they may have unstable angina: pain at rest (which may occur at night), pain on minimal exertion, angina that seems to progress rapidly despite increasing medical treatment. All people with suspected angina should be urgently referred to a chest pain evaluation service, for confirmation of the diagnosis and assessment of the severity of coronary heart disease.

Myocarditis refers to an underlying process that causes inflammation and injury of the heart. It does not refer to inflammation of the heart as a consequence of some other insult. Many secondary causes, such as a heart attack, can lead to inflammation of the myocardium and therefore the diagnosis of myocarditis cannot be made by evidence of inflammation of the myocardium alone.

Myocardial inflammation can be suspected on the basis of electrocardiographic (ECG) results, elevated C-reactive protein (CRP) and/or erythrocyte sedimentation rate (ESR), and increased IgM (serology) against viruses known to affect the myocardium. Markers of myocardial damage (troponin or creatine kinase cardiac isoenzymes) are elevated.

The ECG findings most commonly seen in myocarditis are diffuse T wave inversions; saddle-shaped ST-segment elevations may be present (these are also seen in pericarditis).

The gold standard is still biopsy of the myocardium, in general done in the setting of angiography. A small tissue sample of the endocardium and myocardium is taken, and investigated by a pathologist by light microscopy and—if necessary—immunochemistry and special staining methods. Histopathological features are myocardial interstitium with abundant edema and inflammatory infiltrate, rich in lymphocytes and macrophages. Focal destruction of myocytes explains the myocardial pump failure.

Cardiac magnetic resonance imaging (cMRI or CMR) has been shown to be very useful in diagnosing myocarditis by visualizing markers for inflammation of the myocardium.

Recently, consensus criteria for the diagnosis of myocarditis by CMR have been published.

Nitroglycerin can be used immediately to widen the coronary arteries and help increase blood flow to the heart. In addition, nitroglycerin causes peripheral venous and artery dilation reducing cardiac preload and afterload. These reductions allow for decreased stress on the heart and therefore lower the oxygen demand of the heart's muscle cells.

Antiplatelet drugs such as aspirin and clopidogrel can help reduce the progression of atherosclerotic plaque formation, as well as combining these with an anticoagulant such as a low molecular weight heparin.

Studies have shown no benefit for the use of herbal medicine on all cause mortality in viral myocarditis.

When cardiomyopathy is suspected as the cause of cardiogenic shock, a biopsy of heart muscle may be needed to make a definite diagnosis.

The Swan-Ganz catheter or pulmonary artery catheter may assist in the diagnosis by providing information on the hemodynamics.

In developed countries, with improved public health, infection control and increasing life spans, atheroma processes have become an increasingly important problem and burden for society.

Atheromata continue to be the primary underlying basis for disability and death, despite a trend for gradual improvement since the early 1960s (adjusted for patient age). Thus, increasing efforts towards better understanding, treating and preventing the problem are continuing to evolve.

According to United States data, 2004, for about 65% of men and 47% of women, the first symptom of cardiovascular disease is myocardial infarction (heart attack) or sudden death (death within one hour of symptom onset).

A significant proportion of artery flow-disrupting events occur at locations with less than 50% lumenal narrowing. Cardiac stress testing, traditionally the most commonly performed noninvasive testing method for blood flow limitations, generally only detects lumen narrowing of ~75% or greater, although some physicians advocate nuclear stress methods that can sometimes detect as little as 50%.

The sudden nature of the complications of pre-existing atheroma, vulnerable plaque (non-occlusive or soft plaque), have led, since the 1950s, to the development of intensive care units and complex medical and surgical interventions. Angiography and later cardiac stress testing was begun to either visualize or indirectly detect stenosis. Next came bypass surgery, to plumb transplanted veins, sometimes arteries, around the stenoses and more recently angioplasty, now including stents, most recently drug coated stents, to stretch the stenoses more open.

Yet despite these medical advances, with success in reducing the symptoms of angina and reduced blood flow, atheroma rupture events remain the major problem and still sometimes result in sudden disability and death despite even the most rapid, massive and skilled medical and surgical intervention available anywhere today. According to some clinical trials, bypass surgery and angioplasty procedures have had at best a minimal effect, if any, on improving overall survival. Typically mortality of bypass operations is between 1 and 4%, of angioplasty between 1 and 1.5%.

Additionally, these vascular interventions are often done only after an individual is symptomatic, often already partially disabled, as a result of the disease. It is also clear that both angioplasty and bypass interventions do not prevent future heart attack.

The older methods for understanding atheroma, dating to before World War II, relied on autopsy data. Autopsy data has long shown initiation of fatty streaks in later childhood with slow asymptomatic progression over decades.

One way to see atheroma is the very invasive and costly IVUS ultrasound technology; it gives us the precise volume of the inside intima plus the central media layers of about of artery length. Unfortunately, it gives no information about the structural strength of the artery. Angiography does not visualize atheroma; it only makes the blood flow within blood vessels visible. Alternative methods that are non or less physically invasive and less expensive per individual test have been used and are continuing to be developed, such as those using computed tomography (CT; led by the electron beam tomography form, given its greater speed) and magnetic resonance imaging (MRI). The most promising since the early 1990s has been EBT, detecting calcification within the atheroma before most individuals start having clinically recognized symptoms and debility. Interestingly, statin therapy (to lower cholesterol) does not slow the speed of calcification as determined by CT scan. MRI coronary vessel wall imaging, although currently limited to research studies, has demonstrated the ability to detect vessel wall thickening in asymptomatic high risk individuals. As a non-invasive, ionising radiation free technique, MRI based techniques could have future uses in monitoring disease progression and regression. Most visualization techniques are used in research, they are not widely available to most patients, have significant technical limitations, have not been widely accepted and generally are not covered by medical insurance carriers.

From human clinical trials, it has become increasingly evident that a more effective focus of treatment is slowing, stopping and even partially reversing the atheroma growth process. There are several prospective epidemiologic studies including the Atherosclerosis Risk in Communities (ARIC) Study and the Cardiovascular Health Study (CHS), which have supported a direct correlation of Carotid Intima-media thickness (CIMT) with myocardial infarction and stroke risk in patients without cardiovascular disease history. The ARIC Study was conducted in 15,792 individuals between 5 and 65 years of age in four different regions of the US between 1987 and 1989. The baseline CIMT was measured and measurements were repeated at 4- to 7-year intervals by carotid B mode ultrasonography in this study. An increase in CIMT was correlated with an increased risk for CAD. The CHS was initiated in 1988, and the relationship of CIMT with risk of myocardial infarction and stroke was investigated in 4,476 subjects ≤65 years of age. At the end of approximately six years of follow-up, CIMT measurements were correlated with cardiovascular events.

Paroi artérielle et Risque Cardiovasculaire in Asia Africa/Middle East and Latin America (PARC-AALA) is another important large-scale study, in which 79 centers from countries in Asia, Africa, the Middle East, and Latin America participated, and the distribution of CIMT according to different ethnic groups and its association with the Framingham cardiovascular score was investigated. Multi-linear regression analysis revealed that an increased Framingham cardiovascular score was associated with CIMT, and carotid plaque independent of geographic differences.

Cahn et al. prospectively followed-up 152 patients with coronary artery disease for 6–11 months by carotid artery ultrasonography and noted 22 vascular events (myocardial infarction, transient ischemic attack, stroke, and coronary angioplasty) within this time period. They concluded that carotid atherosclerosis measured by this non-interventional method has prognostic significance in coronary artery patients.

In the Rotterdam Study, Bots et al. followed 7,983 patients >55 years of age for a mean period of 4.6 years, and reported 194 incident myocardial infarctions within this period. CIMT was significantly higher in the myocardial infarction group compared to the other group. Demircan et al. found that the CIMT of patients with acute coronary syndrome were significantly increased compared to patients with stable angina pectoris.

It has been reported in another study that a maximal CIMT value of 0.956 mm had 85.7% sensitivity and 85.1% specificity to predict angiographic CAD. The study group consisted of patients admitted to the cardiology outpatient clinic with symptoms of stable angina pectoris. The study showed CIMT was higher in patients with significant CAD than in patients with non-critical coronary lesions. Regression analysis revealed that thickening of the mean intima-media complex more than 1.0 was predictive of significant CAD our patients. There was incremental significant increase in CIMT with the number coronary vessel involved. In accordance with the literature, it was found that CIMT was significantly higher in the presence of CAD. Furthermore, CIMT was increased as the number of involved vessels increased and the highest CIMT values were noted in patients with left main coronary involvement. However, human clinical trials have been slow to provide clinical & medical evidence, partly because the asymptomatic nature of atheromata make them especially difficult to study. Promising results are found using carotid intima-media thickness scanning (CIMT can be measured by B-mode ultrasonography), B-vitamins that reduce a protein corrosive, homocysteine and that reduce neck carotid artery plaque volume and thickness, and stroke, even in late-stage disease.

Additionally, understanding what drives atheroma development is complex with multiple factors involved, only some of which, such as lipoproteins, more importantly lipoprotein subclass analysis, blood sugar levels and hypertension are best known and researched. More recently, some of the complex immune system patterns that promote, or inhibit, the inherent inflammatory macrophage triggering processes involved in atheroma progression are slowly being better elucidated in animal models of atherosclerosis.

It is critical to diagnose CRS at an early stage in order to achieve optimal therapeutic efficacy. However, unlike markers of heart damage or stress such as troponin, creatine kinase, natriuretic peptides, reliable markers for acute kidney injury are lacking. Recently, research has found several biomarkers that can be used for early detection of acute kidney injury before serious loss of organ function may occur. Several of these biomarkers include neutrophil gelatinase-associated lipocalin (NGAL), N-acetyl-B-D-glucosaminidase (NAG), Cystatin C, and kidney injury molecule-1 (KIM-1) which have been shown to be involved in tubular damage. Other biomarkers that have been shown to be useful include BNP, IL-18, and fatty acid binding protein (FABP). However, there is great variability in the measurement of these biomarkers and their use in diagnosing CRS must be assessed.

Because artery walls enlarge at locations with atheroma, detecting atheroma before death and autopsy has long been problematic at best. Most methods have focused on the openings of arteries; highly relevant, yet totally miss the atheroma within artery walls.

Historically, arterial wall fixation, staining and thin section has been the gold standard for detection and description of atheroma, after death and autopsy. With special stains and examination, micro calcifications can be detected, typically within smooth muscle cells of the arterial media near the fatty streaks within a year or two of fatty streaks forming.

Interventional and non-interventional methods to detect atherosclerosis, specifically vulnerable plaque (non-occlusive or soft plaque), are widely used in research and clinical practice today.

Carotid Intima-media thickness Scan (CIMT can be measured by B-mode ultrasonography) measurement has been recommended by the American Heart Association as the most useful method to identify atherosclerosis and may now very well be the gold standard for detection.

IVUS is the current most sensitive method detecting and measuring more advanced atheroma within living individuals, though it is typically not used until decades after atheroma begin forming due to cost and body invasiveness.

CT scans using state of the art higher resolution spiral, or the higher speed EBT, machines have been the most effective method for detecting calcification present in plaque. However, the atheroma have to be advanced enough to have relatively large areas of calcification within them to create large enough regions of ~130 Hounsfield units which a CT scanner's software can recognize as distinct from the other surrounding tissues. Typically, such regions start occurring within the heart arteries about 2–3 decades after atheroma start developing. Hence the detection of much smaller plaques than previously possible is being developed by some companies, such as Image Analysis. The presence of smaller, spotty plaques may actually be more dangerous for progressing to acute myocardial infarction.

Arterial ultrasound, especially of the carotid arteries, with measurement of the thickness of the artery wall, offers a way to partially track the disease progression. As of 2006, the thickness, commonly referred to as IMT for intimal-medial thickness, is not measured clinically though it has been used by some researchers since the mid-1990s to track changes in arterial walls. Traditionally, clinical carotid ultrasounds have only estimated the degree of blood lumen restriction, stenosis, a result of very advanced disease. The National Institute of Health did a five-year $5 million study, headed by medical researcher Kenneth Ouriel, to study intravascular ultrasound techniques regarding atherosclerotic plaque. More progressive clinicians have begun using IMT measurement as a way to quantify and track disease progression or stability within individual patients.

Angiography, since the 1960s, has been the traditional way of evaluating for atheroma. However, angiography is only motion or still images of dye mixed with the blood with the arterial lumen and never show atheroma; the wall of arteries, including atheroma with the arterial wall remain invisible. The limited exception to this rule is that with very advanced atheroma, with extensive calcification within the wall, a halo-like ring of radiodensity can be seen in most older humans, especially when arterial lumens are visualized end-on. On cine-floro, cardiologists and radiologists typically look for these calcification shadows to recognize arteries before they inject any contrast agent during angiograms.

Due to the acute hemodynamic deterioration associated with myocardial rupture, the diagnosis is generally made based on physical examination, changes in the vital signs, and clinical suspicion. The diagnosis can be confirmed with echocardiography. The diagnosis is ultimately made at autopsy.