Cardiac Catheterization and Coronary Angiography

Hemodynamic technique and monitoring

Specialized catheters and puncture needles are used for the procedure. Access is established via veins (subclavian, basilic) or the femoral artery. Long-term central hemodynamic monitoring requires the use of a "floating" balloon Swan-Ganz catheter (Swan-Ganz).

Technique for placing a Swan-Ganz catheter:

1. A puncture of the subclavian vein is performed.
2. The catheter is advanced through the right atrium and right ventricle into the pulmonary artery.
3. The instrument is advanced as distally as possible into the small branches of the pulmonary artery.

Inflating the balloon at the tip of the catheter blocks blood flow behind it, producing the "wedging" phenomenon. The pressure measured proximal to the balloon is called pulmonary capillary wedge pressure (PCWP or PCW). This parameter indirectly reflects left atrial pressure and is equivalent to left ventricular end-diastolic pressure (LVEDP), provided there is no mitral stenosis.

The catheter may remain in the pulmonary artery from several hours up to a day. This is necessary in shock states, complicated myocardial infarction (ventricular septal or papillary muscle rupture), resistant hypotension, and for the differential diagnosis of cardiogenic and non-cardiogenic pulmonary edema.

Reference values

During catheterization, myocardial performance indexes are assessed. Normally, the cardiac index is 2.5–4.0 L/min/m², and the indexed stroke volume is 40–70 mL/m².

Intracardiac pressure values directly reflect ventricular contractility:

Functional diagnostics (cardiac output and shunts)

Measurement of cardiac output (CO) is performed using the thermodilution method. A fluid of a specific temperature is injected into the bloodstream. A special sensor records the temperature curve, the area under which (relative to the baseline) is proportional to the cardiac output volume.

Diagnosis of intracardiac shunts is based on the analysis of blood oxygen saturation. Normally, venous blood saturation in the right-sided chambers is approximately 75%. If a stepwise increase in oxygen is detected during catheter advancement — for example, saturation in the right ventricle is higher than in the right atrium — this indicates a left-to-right shunting of arterialized blood (in this example, through a ventricular septal defect).

Coronary angiography and interventions

Coronary angiography is the key evaluation method in coronary artery disease (CAD). It is indicated for pain of unclear origin, resistant angina, planning revascularization (CABG or plasty), and complex valvular heart disease. The method allows for identifying the location of the obstruction and its cause: atherosclerotic plaque, thrombosis, or spasm.

Evaluation of stenoses:

• A 75% narrowing is significant even over a short vascular segment.
• A 50% narrowing is significant with a long lesion length.
• A narrowing between 50% and 75% is generally considered hemodynamically significant.
• Spasm, unlike plaque, often involves an extended segment and completely resolves following the administration of nitroglycerin.

Therapeutic maneuvers can be performed immediately during the study: administering thrombolytics, performing valvuloplasty or transluminal balloon angioplasty (with stent placement to prevent restenosis). Laser recanalization is also used — creating microchannels in the ischemic zone to supply the myocardium directly from the ventricle during systole.

Endomyocardial biopsy and complications

Tissue sampling from the left or right ventricle can be performed via the catheter. To obtain a reliable result, material must be harvested from 5–6 different sites. Biopsy is critically important for diagnosing cardiac transplant rejection, detecting infiltrative processes (amyloidosis, hemochromatosis), and differentiating myocarditis from congestive cardiomyopathy.

Despite high safety, catheterization carries the risk of complications: myocardial infarction, vessel dissection or rupture, thrombophlebitis, pneumothorax (during vein puncture), carotid artery injury, and neurological disorders.

Briefly: answers to topical questions

What else to study on this topic

• Mathematical calculation of intracardiac shunt volume based on cardiac output.
• Differential diagnosis of cardiogenic and non-cardiogenic pulmonary edema based on filling pressures.
• Mechanism of laser recanalization and the physiology of myocardial blood supply during systole.
• Complications of myocardial infarction (septal rupture, papillary muscle avulsion) and indications for emergency hemodynamic support.

Other topics in the "Cardiovascular system" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.