Complications of Cardiac Catheterization

Vascular Access Complications (Arterial Injury Mechanisms)

• Mechanical vessel trauma: Direct laceration or perforation of the access artery (femoral, radial, brachial) during puncture causes intimal injury, exposing thrombogenic subendothelial tissue and activating the coagulation cascade
• Intimal dissection: Longitudinal separation of the arterial intima from the media by guidewire or catheter creates a false lumen, restricting true lumen flow and triggering platelet aggregation and thrombus formation
• Vasospasm: Endothelial irritation releases vasoconstrictor mediators (endothelin, catecholamines), particularly prevalent with radial access, causing transient or persistent vessel narrowing
• Hematoma formation: Transmural arterial perforation allows blood extravasation into surrounding tissue planes; expanding hematomas compress adjacent structures and create pseudoaneurysms when confined by fascial layers
• Pseudoaneurysm pathophysiology: Arterial defect contained by surrounding soft tissue creates a cavity communicating with the arterial lumen; systolic pressure maintains flow into this space while diastolic pressure pushes blood back into the artery, creating a "to-and-fro" flow pattern

Contrast-Induced Nephropathy (CIN) Mechanisms

• Direct tubular toxicity: Hyperosmolar contrast agents (osmolality 600-2000 mOsm/kg) damage proximal tubular epithelial cells through dehydration and cellular apoptosis; iodinated contrast is filtered at the glomerulus and concentrated in tubular fluid, increasing local osmolarity
• Renal hemodynamic alterations: Initial renal vasodilation followed by sustained vasoconstriction reduces renal blood flow and glomerular filtration rate; contrast-induced adenosine release and increased local oxygen demand paradoxically create a state of renal hypoxia despite systemic hemodynamic stability
• Oxidative stress: Contrast agents generate reactive oxygen species (ROS) that overwhelm endogenous antioxidant defense systems (superoxide dismutase, catalase); enhanced in patients with diabetes, pre-existing renal disease, and dehydration
• Viscosity-related factors: High-osmolarity contrast increases blood viscosity, worsening renal perfusion in already compromised kidneys; this mechanism is less prominent with iso-osmolar contrast media (IOCM)

Coronary Artery Perforation Mechanisms

• Guidewire-induced transmural injury: Perforation occurs when a rigid or hydrophilic guidewire traverses a diseased arterial segment with loss of normal elastic recoil; histology shows full-thickness breach with disruption of internal elastic lamina and media
• Vessel dissection extension: Aggressive balloon inflation in a setting of pre-existing dissection can propagate the dissection plane transmurally, converting a contained intimal injury into frank perforation
• Mechanical plunge: Abrupt deep seating of guide catheters into small caliber vessels or penetration into side branches causes acute transmural injury with immediate hemorrhage into the pericardial space

Tamponade Pathophysiology

• Pericardial fluid accumulation: Rapid bleeding from coronary perforation fills the pericardial sac with blood; the pericardium's limited compliance means even modest volumes (150-200 mL) can cause hemodynamic compromise
• Equalization of diastolic pressures: Intrapericardial pressure rises and compresses all four cardiac chambers; ventricular filling becomes impaired, causing equalization of right atrial (RA), right ventricular (RV), pulmonary artery diastolic (PAD), and pulmonary capillary wedge pressures (PCWP)
• Reduced cardiac output: Both preload (venous return) and afterload mechanisms fail; decreased ventricular filling reduces stroke volume, while elevated intrapericardial pressure increases effective afterload, creating a double hit on cardiac output

Arrhythmia Induction Mechanisms

• Mechanical irritation: Catheter contact with atrial or ventricular myocardium triggers ectopic activity; contact with the RV outflow tract or left main coronary ostium carries particular arrhythmia risk
• Ischemia during coronary ostium instrumentation: Temporary occlusion of coronary arteries (especially the left main) during catheter manipulation can induce acute regional ischemia with both atrial and ventricular ectopy
• Electrolyte shifts: Contrast agent administration causes osmotic shifts affecting serum potassium and magnesium; hypocalcemia from citrate in blood products during transfusion may prolong QT interval

Vascular Access Site Complications

• Mechanical causes: Puncture of artery anterior or posterior wall (inadvertent), multiple puncture attempts, use of larger caliber sheaths (>7 French), inadequate hemostasis after sheath removal, anticoagulation effects (heparin, warfarin, dual antiplatelet therapy)
• Patient factors increasing risk: Advanced age (>75 years), female gender (smaller vessel caliber), low body surface area, peripheral vascular disease (atherosclerotic disease, aortic aneurysm, prior intervention), chronic kidney disease, diabetes mellitus, hypertension, obesity
• Procedural factors: Emergent intervention (STEMI), prolonged procedure duration, increased contrast volume, complex intervention requiring multiple catheters or prolonged guidewire manipulation
• Access site selection: Femoral access carries higher vascular complication rates (2-3%) compared to radial access (0.5-1%), though radial access has steeper learning curve and higher vasospasm rates

Contrast-Induced Nephropathy

• Patient-related risk factors: Chronic kidney disease (baseline eGFR <60 mL/min/1.73 m², particularly <30), diabetes mellitus (synergistic effect with CKD), advanced age (>70 years), congestive heart failure (cardiorenal syndrome), volume depletion, sepsis, concurrent nephrotoxic medications (NSAIDs, ACE inhibitors/ARBs, aminoglycosides, NSAIDs)
• Procedural factors: High contrast volume (volume of contrast >eGFR ratio of >3.7 is high-risk), type of contrast (high-osmolarity agents > low-osmolarity > iso-osmolar), osmolarity and viscosity of agent
• Anemia: Hemoglobin <10 g/dL impairs oxygen delivery to renal tubules, worsening hypoxia-induced injury

Coronary Artery Perforation

• Procedural factors: Aggressive balloon angioplasty (particularly in calcified lesions), oversizing balloons relative to vessel diameter, repeat inflations in same location, use of cutting or scoring balloons in eccentric lesions, rotational atherectomy (highest risk at 0.5-1%), laser angioplasty, brachytherapy
• Lesion characteristics: Severe calcification (provides less elastic recoil), tortuous vessels, in-stent restenosis requiring aggressive dilatation, chronic total occlusions with collateral-dependent myocardium
• Patient factors: Older age, female gender, small vessel size, severe left ventricular dysfunction with dependence on specific vessel

Atrial Septal Defect (ASD) and Patent Foramen Ovale (PFO) Creation

• Transseptal puncture complications: Traumatic creation of ASD from aggressive needle advancement, use of excessively rigid dilators, inadvertent perforation of posterior septum or aortic root during transseptal puncture

Infection

• Bacterial contamination: Inadequate sterile technique, prolonged procedure duration, femoral access (higher bacterial colonization rate than radial), immunocompromised patients
• Organisms: Staphylococcus aureus (including MRSA), coagulase-negative staphylococci, gram-negative rods (Klebsiella, Pseudomonas), fungal organisms in severely immunocompromised hosts

Radiation Exposure

• Procedural factors: Prolonged fluoroscopy time (especially with frame rates >15 frames/second), multiple projections, operator technique (distance from radiation source, fluoroscopy time management), lack of shielding
• Patient factors: Obesity increases scatter radiation and fluoroscopy time requirement

Vascular Access Site Complications

• Cardinal symptoms: Localized pain and swelling at access site, often appearing immediately after sheath removal or within hours
• Physical examination: Palpable swelling, warmth, ecchymosis (bruising) that may extend along fascial planes; pain on palpation
• Associated findings: May be painless if small (<5 cm), typically self-limited if uncomplicated

• Cardinal symptoms: Continuous pain at access site, pulsatile mass (patient may feel or hear a "heartbeat" in the groin), coolness or paresthesias if distal vessel compression occurs
• Physical examination: "To-and-fro" flow on palpation (classic finding—pulsatile expansion during systole and contraction during diastole), audible bruit on auscultation, systolic flow on Doppler ultrasound
• Limb-threatening findings: Foot coolness, color change (pallor or cyanosis), decreased pulses, inability to move toes, signs of compartment syndrome

• Cardinal symptoms: Localized warmth, continuous machinery-like murmur on exam (machine-like quality distinguishes from pseudoaneurysm bruit)
• Physical examination: Continuous "machinery" murmur on auscultation, hyperdynamic pulses distally, possible signs of steal physiology (limb claudication if severe)
• Hemodynamic findings: Wide pulse pressure (elevated systolic, decreased diastolic) if large shunt

• Cardinal symptoms: Acute onset limb pain, coolness, pallor, paresthesias, or claudication in the distribution of the access artery (foot in femoral access, hand in radial access)
• Physical examination: Diminished or absent pulses distal to access site, cool extremity, mottled skin, weak or absent motor function
• Critical findings: Severe pain disproportionate to examination findings (suggests developing compartment syndrome)

Contrast-Induced Nephropathy

• Timing: Acute kidney injury developing 24-72 hours after contrast exposure (can occur up to 7 days)
• Cardinal symptoms: Often asymptomatic, detected only on laboratory abnormalities; if severe, may present with oliguria (urine output <400 mL/day), nausea, fatigue
• Laboratory presentation: Serum creatinine elevation (usually peaks at 3-5 days), elevated BUN, elevated potassium if oliguric, elevated phosphate
• Risk factors for progression to requiring dialysis: Pre-existing eGFR <30 mL/min/1.73 m², diabetes with eGFR <60, class IV heart failure, large contrast volumes, multiple exposures in short time period

Coronary Artery Perforation

• Timing of onset: Immediate (during procedure) to delayed (hours later if small perforation with contained rupture)
• Cardinal symptoms: Sudden severe chest pain (often described as "tearing" or "ripping"), chest pressure, dyspnea, diaphoresis, sense of impending doom
• Physical examination findings: Hypotension (may be rapidly progressive), tachycardia, muffled heart sounds (if developing tamponade), pulsus paradoxus (>10 mmHg decrease in systolic pressure with inspiration), elevated JVD (especially if tamponade develops), signs of shock
• Classic presentation: Sudden hemodynamic collapse during or immediately after aggressive balloon inflation, especially in calcified lesions or during rotational atherectomy
• Electrocardiographic findings: ST-segment elevation in distribution of perforated vessel, diffuse ST-segment changes if tamponade develops

Tamponade (From Coronary Perforation or Aortic Root Injury)

• Cardinal symptoms: Acute dyspnea, chest pain, syncope, sudden hemodynamic collapse
• Physical examination: Beck's triad: hypotension, muffled heart sounds, elevated JVD
• Hemodynamic findings: Pulsus paradoxus (>10 mmHg systolic blood pressure drop with inspiration), equalization of diastolic pressures on right and left heart catheterization
• Electrical alternans: Alternating amplitude of QRS complexes on ECG from swinging heart motion in pericardial fluid
• Rapid progression: Can develop within minutes of perforation; time from symptom onset to cardiovascular collapse may be <1 hour

Arrhythmias During Catheterization

• Atrial fibrillation: Palpitations, hypotension if rapid ventricular response, loss of atrial systole
• Ventricular ectopy: Felt as palpitations or irregular heartbeat, may progress to sustained ventricular tachycardia (VT) or ventricular fibrillation (VF)
• Bradycardia: Hypotension, lightheadedness; may occur with right coronary ostium engagement (vagal response) or atrioventricular block from left main manipulation

Infection (Catheterization-Associated)

• Acute presentation (within 24-72 hours): Fever, localized cellulitis (erythema, warmth, fluctuance) at access site, purulent drainage from puncture site, regional lymphadenopathy
• Delayed presentation (>7 days): Endocarditis (new or changing murmur, fever, positive blood cultures, septic emboli), osteomyelitis (bone pain, localized swelling), systemic sepsis
• Prosthetic material infection: Pseudo-aneurysm with infected thrombus may require surgical intervention

Retroperitoneal Hemorrhage (Femoral Access Complication)

• Cardinal symptoms: Severe low back pain (often the only presenting symptom), flank pain, abdominal pain, hypotension, signs of hypovolemia
• Physical examination: Ecchymosis in flank or groin area (may be delayed in appearing, hours after procedure), abdominal distension, signs of hemorrhagic shock
• Laboratory findings: Hemoglobin drop, elevated creatinine from rhabdomyolysis (compression injury)
• Classic trap: Patient may lack typical hematoma findings at access site because bleeding tracks into retroperitoneum rather than superficially

Contrast Allergy/Anaphylaxis

• Immediate symptoms (minutes): Urticaria, angioedema, bronchospasm, hypotension, tachycardia, arrhythmias
• Delayed reactions (hours): Rash, fever, arthralgia (more common with high-osmolarity agents)

Vascular Access Site Complications

• Hematoma: Clinical diagnosis based on pain and swelling; ultrasound used to measure size and confirm simple hematoma (hypoechoic fluid collection without internal flow) vs. pseudoaneurysm
• Pseudoaneurysm:
• Gold standard: Duplex ultrasound showing "to-and-fro" flow pattern with neck diameter measurement (typically <6 mm neck can be observed, >6 mm or enlarging requires intervention)
• Color Doppler shows systolic flow into aneurysm sac and diastolic flow back into artery
• CT angiography or conventional angiography reserved for cases where ultrasound inconclusive or when surgical planning needed
• Arterial dissection/occlusion:
• Contrast angiography (via contralateral limb or transaxillary approach) shows narrowing or abrupt cutoff
• CT angiography can identify intimal flap and true

Immediate stabilisation (procedural emergencies)

• Tamponade from coronary perforation: stop the procedure, give isotonic crystalloid to support preload, and perform echo-guided pericardiocentesis — drainage is the definitive haemodynamic manoeuvre, not vasopressors. Simultaneously reverse anticoagulation (protamine for unfractionated heparin) unless a fresh stent makes reversal prohibitive.
• Sealing the perforation: prolonged low-pressure balloon inflation proximal to the tear is first; escalate to a covered (PTFE) stent for large-vessel (Ellis type III) perforation, or coil/fat/thrombin embolisation for distal wire perforation. Emergency cardiac surgery is definitive when bleeding cannot be sealed percutaneously.
• Arrhythmia: per AHA ACLS, immediate defibrillation for the shockable pair ventricular fibrillation / pulseless VT; atropine plus fluids for the vagally mediated bradycardia–hypotension seen with sheath removal.
• Contrast anaphylaxis: epinephrine 0.3 mg IM first, per the ACR Manual on Contrast Media; antihistamines and corticosteroids are adjuncts and never substitute for epinephrine.

Access-site complications

• Overt bleeding/hematoma: manual or mechanical compression; hold antithrombotics, transfuse for haemodynamic instability.
• Retroperitoneal hemorrhage: resuscitate, reverse anticoagulation, transfuse; escalate to balloon tamponade or covered stent, then surgical repair if bleeding persists.
• Pseudoaneurysm: small ones often thrombose spontaneously; otherwise ultrasound-guided thrombin injection (or compression). Avoid thrombin in a wide-neck lesion, an AV fistula, or an infected sac — distal embolisation or seeding results.
• Acute limb ischaemia/occlusive dissection: systemic heparin plus urgent vascular surgery for thrombectomy or repair.
• Radial spasm: intra-arterial vasodilators (calcium channel blocker, e.g., verapamil, ± nitroglycerin).

Contraindicated / not recommended

• N-acetylcysteine and sodium bicarbonate: no benefit over saline (PRESERVE trial); do not order them reflexively.
• Sheath removal at a supratherapeutic ACT and puncture above the inguinal ligament — both drive retroperitoneal bleeding.
• Nephrotoxins (NSAIDs, aminoglycosides) periprocedurally; hold metformin after contrast in advanced CKD per ACR — to prevent lactic acidosis, not nephropathy.
• Prevention note: the 2021 ACC/AHA/SCAI revascularization guideline recommends radial access to reduce bleeding and vascular complications.

Emergencies (recognise within minutes)

• Cardiac tamponade: perforation bleeds into a non-compliant pericardium; signalled by abrupt hypotension with tachycardia, rising right atrial pressure, and a stationary cardiac silhouette border on fluoroscopy before echo confirms effusion.
• Retroperitoneal hemorrhage: high femoral puncture bleeds into a space that cannot tamponade itself; signalled by hypotension plus flank/back pain with an unremarkable groin — the classic trap.
• Acute limb ischaemia: dissection flap or occlusive thrombus at the access artery; signalled by a pulseless, cool, painful extremity.
• Abrupt vessel closure / stent thrombosis: dissection or platelet-rich thrombus occludes the treated segment; signalled by recurrent ischaemic chest pain with ST elevation in the treated territory.
• Anaphylactoid contrast reaction: direct mast-cell degranulation (not IgE-mediated); signalled by urticaria progressing to bronchospasm and shock.
• VF / pulseless VT: ischaemia or mechanical myocardial irritation; signalled by sudden collapse on the table.

Non-emergent but exam-favoured

• Pseudoaneurysm: contained arterial defect; to-and-fro Doppler flow and a pulsatile mass with systolic bruit.
• Arteriovenous fistula: simultaneous arterial and venous puncture; continuous machinery murmur.
• Cholesterol (atheroembolic) embolisation: catheter scraping of an atherosclerotic aorta showers cholesterol crystals days to weeks later; blue toe syndrome with palpable pulses, livedo reticularis, eosinophilia, hypocomplementemia, and subacute renal decline — distinguishing it from contrast nephropathy.
• Contrast-associated AKI: tubular toxicity plus medullary hypoxia; non-oliguric creatinine rise at 24–72 hours with a bland sediment.
• Periprocedural stroke: air or atheroembolism from catheter exchange; focal deficit on emergence.
• Femoral neuropathy: hematoma compressing the femoral nerve; quadriceps weakness and anteromedial thigh numbness.
• Radiation injury: deterministic skin dose effect; a squared erythematous or ulcerated back/flank patch weeks later.
• Access-site infection: Staphylococcus aureus predominates; purulence, fever, and bacteraemia — MRSA coverage with vancomycin is dosed to a 24-hour AUC targeting AUC/MIC 400–600 per the 2020 IDSA/ASHP consensus.
• Treatment-related: protamine reaction (hypotension, pulmonary hypertension), thrombin-injection embolisation, pericardiocentesis-induced chamber laceration, covered-stent side-branch occlusion, heparin-induced thrombocytopenia.

• Hypotension + back or flank pain after femoral access, groin looks fine: think retroperitoneal hemorrhage. Best next step is resuscitation with reversal of anticoagulation and a non-contrast CT of the abdomen/pelvis; the distractor is a benign groin hematoma.
• Pulsatile mass with a systolic bruit = pseudoaneurysm (to-and-fro Doppler); continuous machinery murmur = arteriovenous fistula. Duplex ultrasound is the single best next test for either.
• Blue toes with intact pedal pulses, livedo reticularis, eosinophilia, and creatinine rising over weeks = cholesterol embolisation. The examiners' contrast is contrast-associated AKI, which peaks at 24–72 hours, has a bland sediment, and never causes eosinophilia.
• Sudden hypotension with jugular venous distension during aggressive balloon inflation or atherectomy = perforation with tamponade. Echo-guided pericardiocentesis first; protamine reversal and balloon/covered-stent sealing follow.
• Radial over femoral access reduces access-site bleeding and vascular complications — a Class 1 recommendation in the 2021 ACC/AHA/SCAI revascularization guideline. Radial's trade-off is spasm, treated with intra-arterial vasodilators.
• Contrast reaction: give epinephrine 0.3 mg IM for anaphylaxis (ACR Manual on Contrast Media). Two distractors — "shellfish allergy" does not predict contrast reactions, and steroid/antihistamine premedication is for elective repeat exposure in a prior reactor, not for acute rescue.
• Metformin is held after contrast in advanced CKD to avoid lactic acidosis, not to prevent nephropathy; N-acetylcysteine and bicarbonate infusions are not effective prophylaxis (PRESERVE). Isotonic saline plus contrast minimisation is the answer.
• Rhythm pearl: the shockable pair is ventricular fibrillation / pulseless VT — defibrillate immediately per AHA ACLS. Vagal bradycardia during sheath removal, by contrast, responds to atropine and fluids.