Cardiac Catheterization

Cardiac catheterisation is the invasive assessment of cardiac anatomy, haemodynamics and function through catheters advanced into the heart and great vessels. It includes left heart catheterisation (coronary angiography and ventriculography), right heart catheterisation, and therapeutic procedures such as PCI, valvuloplasty, structural intervention and ablation.

Access routes

• Radial artery is the preferred route, particularly in acute coronary syndrome, because it lowers access-site bleeding and mortality, and allows immediate mobilisation. Radial artery occlusion occurs in 2 to 10%, usually silent.
• Femoral artery is used for large-bore devices, complex interventions, failed radial access and mechanical support. Ultrasound-guided puncture of the common femoral artery over the femoral head, below the inguinal ligament, reduces complications.
• Brachial and ulnar are alternatives.
• Right heart: femoral vein, internal jugular vein (preferred for pulmonary artery catheters), or antecubital vein.

Indications

• Diagnostic: suspected or known coronary disease with high-risk features, acute coronary syndromes, unexplained heart failure or cardiomyopathy, pre-operative evaluation before valve surgery, ventricular arrhythmia or resuscitated cardiac arrest, and assessment for transplantation.
• Right heart: pulmonary hypertension, shunts, constrictive and restrictive physiology, valvular disease, heart failure with unexplained congestion, and transplant and device candidacy.
• Therapeutic: PCI, balloon valvuloplasty, transcatheter aortic valve implantation, mitral and tricuspid edge-to-edge repair, closure of septal defects and appendage occlusion, alcohol septal ablation, pericardiocentesis and endomyocardial biopsy.

Contraindications are relative and include

• Decompensated heart failure or uncontrolled arrhythmia, active bleeding, uncorrected coagulopathy (INR above 1.8 to 2.0 for femoral access), acute kidney injury, fever or sepsis, severe contrast allergy not yet premedicated, and electrolyte disturbance. Most can be overridden in emergencies.

Complication rates for diagnostic procedures

• Death 0.1%, myocardial infarction under 0.1%, stroke 0.05 to 0.1%, major bleeding 0.2 to 1%, vascular complications 0.5 to 2%, contrast nephropathy 2 to 15% depending on baseline risk, and allergic reactions under 0.5%.
• Perforation, tamponade, arrhythmia, coronary dissection, air embolism, cholesterol embolism, and radiation injury are rare.

Patients are assessed before and after the procedure for features that influence safety.

Preprocedural assessment

• Indication and urgency, symptoms, allergy history (contrast, latex, iodine, shellfish allergy does not predict contrast reaction), renal function, anticoagulant and antiplatelet use, diabetes medication (metformin, SGLT2 inhibitors), pregnancy and pacemaker status.
• Peripheral pulses, Allen test or Doppler for radial perfusion, access site inspection, and bleeding history.
• Risk factors for contrast nephropathy: eGFR under 45 mL/min/1.73 m2 (especially under 30), diabetes, heart failure, hypotension, anaemia, age over 75 and large contrast volume.

Postprocedural features requiring prompt action

• Access-site haematoma: swelling, pain and firmness. A radial forearm haematoma may progress to compartment syndrome, so check pulse, sensation and tension.
• Retroperitoneal haemorrhage: following high femoral puncture, with flank or back pain, hypotension, tachycardia and falling haemoglobin, often after a delay.
• Pseudoaneurysm: pulsatile mass with systolic bruit. Arteriovenous fistula: continuous machinery murmur.
• Limb ischaemia or radial artery occlusion: cold, pale hand or leg, with absent pulse.
• Chest pain or ECG changes: coronary dissection, spasm, thrombosis or air embolism.
• Hypotension with chest pain: tamponade from perforation, or retroperitoneal bleeding.
• Stroke symptoms: emboli or air.
• Contrast reaction: urticaria, bronchospasm, hypotension or anaphylaxis.
• Contrast nephropathy: creatinine rise of 0.3 mg/dL or 50% within 48 to 72 hours, peaking at 3 to 5 days.
• Infection or fever: access-site infection or endocarditis (rare).

Pre-procedure investigations

• ECG, CBC, creatinine and eGFR, electrolytes (potassium), INR and aPTT, group and save for complex procedures, HbA1c, and pregnancy test where relevant.
• Echocardiography when available, and a review of previous coronary CT and stress studies.
• Informed consent, including risks, alternatives and the possibility of proceeding to PCI.

Information obtained

• Coronary angiography: lesion location, severity (percentage diameter stenosis, 70% or more significant in an epicardial vessel and 50% or more in the left main), calcification, thrombus, dissection, collaterals, TIMI flow grade (0 to 3), and dominance. Visual estimation overestimates lesion severity in intermediate stenoses.
• Physiological assessment: fractional flow reserve of 0.80 or less (pressure wire, adenosine 140 micrograms/kg/min IV or 100 to 200 micrograms intracoronary bolus) or instantaneous wave-free ratio of 0.89 or less indicates significant ischaemia. Intravascular ultrasound (minimum lumen area under 6 mm2 for left main) and optical coherence tomography define plaque morphology and optimise stent sizing.
• Left ventriculography: ejection fraction, regional wall motion and mitral regurgitation. Left ventricular end-diastolic pressure above 18 mmHg indicates elevated filling pressure.
• Aortography: aortic regurgitation, aortic root disease and coarctation.

Right heart catheterisation measurements (normal values)

• Right atrial pressure: mean 2 to 6 mmHg.
• Right ventricle: systolic 15 to 30 mmHg, end-diastolic 2 to 8 mmHg.
• Pulmonary artery: systolic 15 to 30, diastolic 4 to 12, mean 9 to 18 mmHg. Pulmonary hypertension is a mean pressure above 20 mmHg.
• Pulmonary artery wedge pressure: 6 to 12 mmHg, with 15 mmHg or less excluding left heart disease as a cause of pulmonary hypertension.
• Cardiac output by thermodilution (unreliable with severe tricuspid regurgitation or low output, or intracardiac shunt) or by Fick (using oxygen consumption). Normal cardiac index is 2.5 to 4.0 L/min/m2.
• Pulmonary vascular resistance = (mean pulmonary artery pressure minus wedge pressure) divided by cardiac output. Normal is under 2 Wood units. Pulmonary arterial hypertension requires a mean pulmonary artery pressure above 20 mmHg, wedge pressure of 15 mmHg or less, and pulmonary vascular resistance above 2 Wood units.
• Shunt calculation by oximetry run: a step up in saturation of 7% or more between chambers indicates a left to right shunt, and a Qp:Qs ratio above 1.5 usually indicates a haemodynamically significant shunt.
• Vasodilator testing (inhaled nitric oxide 20 to 40 ppm, or epoprostenol) identifies vasoreactivity in pulmonary arterial hypertension (a fall in mean pressure of 10 mmHg or more to under 40 mmHg with preserved cardiac output).
• Valve assessment: aortic valve area by the Gorlin or Hakki formula, using simultaneous left ventricular and aortic pressures. Aortic stenosis is severe when the area is under 1.0 cm2.
• Constriction versus restriction: ventricular interdependence (discordant respiratory variation of right and left ventricular systolic pressures) favours constrictive pericarditis, whereas concordant changes with high pulmonary artery systolic pressure favour restrictive cardiomyopathy.

Special provocation: intracoronary acetylcholine (20, 50, 100 micrograms) for vasospasm, with intracoronary nitroglycerin 100 to 200 micrograms to reverse it.

Before the procedure

• Fast for solids 6 hours (clear fluids permitted), with continuation of aspirin and statins and antihypertensives. Continue clopidogrel or ticagrelor if recent stent.
• Metformin: withhold on the day for eGFR under 30 or acute kidney injury, and for 48 hours after contrast when eGFR is 30 to 60 with additional risk. SGLT2 inhibitors are stopped 3 days before elective procedures.
• Warfarin: radial access can be done at INR 3 or below, whereas femoral access prefers INR under 1.8. DOACs: hold 24 to 48 hours for femoral procedures (longer in renal impairment), and many centres proceed radially with a 12 to 24 hour omission.
• Contrast allergy premedication for prior moderate to severe reactions: prednisone 50 mg orally at 13, 7 and 1 hour before the procedure plus diphenhydramine 50 mg 1 hour before, or methylprednisolone 32 mg orally 12 and 2 hours before. In urgent cases use hydrocortisone 200 mg IV with diphenhydramine 50 mg IV 1 hour before.
• Contrast nephropathy prevention: isotonic saline at 1 mL/kg/h (0.5 mL/kg/h if ejection fraction under 35% or heart failure) for 3 to 12 hours before and 6 to 12 hours after, or left ventricular end-diastolic pressure-guided hydration. Use iso-osmolar or low-osmolar contrast, minimise volume (aim for contrast volume to eGFR ratio below 2 to 3), avoid repeated contrast within 72 hours, withhold NSAIDs and diuretics, and consider high-intensity statin. Acetylcysteine and sodium bicarbonate add no proven benefit.

During the procedure

• Local anaesthesia with lidocaine 1 to 2% (2 to 5 mL), mild sedation with midazolam 0.5 to 2 mg and fentanyl 25 to 50 micrograms if needed.
• Radial spasm prevention: verapamil 2.5 to 5 mg intra-arterial, or nitroglycerin 100 to 200 micrograms intra-arterial, mixed with heparin.
• Anticoagulation: heparin 50 to 70 units/kg (3,000 to 5,000 units) via radial access in diagnostic procedures (reduces radial occlusion), and 70 to 100 units/kg for PCI (target ACT 250 to 300 seconds). Bivalirudin 0.75 mg/kg bolus then 1.75 mg/kg/h is an alternative.
• Antiplatelet loading for PCI: aspirin 300 mg, plus clopidogrel 600 mg, ticagrelor 180 mg or prasugrel 60 mg depending on setting.
• Minimise radiation exposure and contrast volume.

After the procedure

• Radial: compression band for 2 to 4 hours, with patent haemostasis technique, and mobilise early. Check the radial pulse and ulnar flow. Avoid repeat radial puncture of an occluded artery.
• Femoral: manual compression or a vascular closure device. Bed rest with the leg straight for 2 to 4 hours (up to 6 hours after sheath removal in large sheaths), with groin and pulse checks.
• Oral and IV hydration, creatinine at 48 to 72 hours in patients at risk, and restart held medicines (metformin after renal function is confirmed stable).
• Resume anticoagulation per procedure risk, often within 6 to 24 hours after sheath removal.
• Discharge same day for uncomplicated diagnostic radial procedures, and observation overnight after PCI or for femoral access in high-risk patients.

Management of complications

• Bleeding and haematoma: direct pressure, reversal as needed (protamine 1 mg per 100 units of heparin), and blood transfusion if haemoglobin falls. Radial forearm haematoma needing urgent compression with a blood pressure cuff inflated above systolic pressure and surgical evacuation for compartment syndrome.
• Retroperitoneal haemorrhage: stop anticoagulants, resuscitate with blood products, perform CT, and use balloon tamponade or covered stent or surgical repair for ongoing bleeding.
• Femoral pseudoaneurysm: ultrasound-guided compression for small lesions, ultrasound-guided thrombin injection (500 to 1,000 units) into the sac for those with a narrow neck, and surgical repair for large, infected or failed cases.
• Arteriovenous fistula: observation if small, covered stent or surgery for symptomatic shunt.
• Radial artery occlusion: prevention by adequate heparin and patent haemostasis. Treat acute symptomatic occlusion with ipsilateral ulnar compression, anticoagulation (rivaroxaban 15 mg daily for 4 weeks in some protocols) for symptoms.
• Coronary dissection or perforation: stent for flow-limiting dissection. Perforation needs prolonged balloon inflation, heparin reversal, covered stent or coil embolisation, and urgent pericardiocentesis for tamponade.
• Coronary spasm: intracoronary nitroglycerin 100 to 200 micrograms.
• Air embolism: 100% oxygen, aspiration of the air, and supportive therapy.
• Contrast reaction: mild urticaria managed with diphenhydramine 25 to 50 mg IV. Anaphylaxis needs epinephrine 0.5 mg intramuscularly (0.5 mL of 1 mg/mL), IV fluids, oxygen, and nebulised salbutamol and steroids for bronchospasm.
• Contrast nephropathy: supportive management, with volume optimisation, avoidance of further nephrotoxins and renal replacement therapy for standard indications.
• Cholesterol embolism: supportive management, as outlined for cholesterol embolization syndrome.
• Stroke: emergency imaging with thrombectomy where indicated.
• Vasovagal reaction: atropine 0.5 to 1 mg IV and leg elevation.

Quality measures include a radial access rate above 80% in acute coronary syndrome, door to balloon time under 90 minutes in STEMI, and monitoring of radiation dose and contrast volume.