Other, non-invasive tests are better used when the diagnosis or certainty of the diagnosis is not as clear.Indications for cardiac catheterization include the following:
Acute coronary syndromes: ST elevation MI (STEMI), non-ST Elevation MI (NSTEMI), and unstable angina
Evaluation of coronary artery disease as indicated by
Abnormal stress test
As part of the pre-op evaluation for other cardiac procedures (e.g., valve replacement) as coronary artery bypass grafting may be done at the same time
Risk stratification for high cardiac risk surgeries (e.g., endovascular aneurysm repair)
Persistent chest pain despite medical therapy thought to be cardiac in origin
New-onset unexplained heart failure
Survival of sudden cardiac death or dangerous cardiac arrhythmias
Workup of suspected Prinzmetal angina (coronary vasospasm)Right heart catheterization, along with pulmonary function testing and other testing should be done to confirm pulmonary hypertension prior to having vasoactive pharmacologic treatments approved and initiated. to measure intracardiac and intravascular blood pressures
to take tissue samples for biopsy
to inject various agents for measuring blood flow in the heart; also to detect and quantify the presence of an intracardiac shunt
to inject contrast agents in order to study the shape of the heart vessels and chambers and how they change as the heart beats

Pacemakers and defibrillators
Placement of internal pacemakers and defibrillators are done through catheterization as well. An exception to this is placement of electrodes on the outer surface of the heart (called epicardial electrodes). Otherwise, electrodes are placed through the venous system into the heart and left there permanently.
LHC can be synonymous with coronary angiography.technique is also used to assess the amount of occlusion (or blockage) in a coronary artery, often described as a percentage of occlusion. A thin, flexible wire is inserted into either the femoral artery or the radial artery and threaded toward the heart until it is in the ascending aorta. Radial access is not associated with an increased risk of stroke over femoral access. At this point, a catheter is guided over the wire into the ascending aorta, where it can be maneuvered into the coronary arteries through the coronary ostia. In this position, the interventional cardiologist can inject contrast and visualize the flow through the vessel. If necessary, the physician can utilize percutaneous coronary intervention techniques, including the use of a stent (either bare-metal or drug-eluting) to open the blocked vessel and restore appropriate blood flow. In general, occlusions greater than 70% of the width of the vessel lumen are thought to require intervention. However, in cases where multiple vessels are blocked (so-called "three-vessel disease"), the interventional cardiologist may opt instead to refer the patient to a cardiothoracic surgeon for coronary artery bypass graft (CABG; see Coronary artery bypass surgery) surgery. Right heart catheterization
Right heart catheterization (RHC) allows the physician to determine the pressures within the heart (intracardiac pressures). The heart is most often accessed via the internal jugular or femoral vein; arteries are not used. Values are commonly obtained for the right atrium, right ventricle, pulmonary artery, and pulmonary capillary "wedge" pressures.