Acute Left Atrial Appendage Thrombus Formation During Transcatheter Mitral Valve Edge-to-Edge Repair.

We present a case of a 75-year-old man who developed an acute left atrial appendage thrombus immediately following mitral valve transcatheter edge to edge repair despite adequate intraprocedural anticoagulation. The patient was managed with enoxaparin to warfarin bridging with no obvious thromboembolic events on follow-up. Attention to anticoagulation is important to reduce thromboembolic risk during mitral valve transcatheter edge to edge repair. (Level of Difficulty: Intermediate.).

Incidence, Predictors, and Outcomes of Endocarditis After Transcatheter Aortic Valve Replacement in the United States.

OBJECTIVES: This study sought to evaluate the incidence and outcomes of endocarditis after transcatheter aortic valve replacement (TAVR). BACKGROUND: Data about endocarditis after TAVR are limited. METHODS: The study investigated Medicare patients who underwent TAVR from 2012 to 2017 and identified patients admitted with endocarditis during follow-up using a validated algorithm. The main study outcome was all-cause mortality. RESULTS: Of 134,717 patients who underwent TAVR, 1868 patients developed endocarditis during follow-up (incidence 0.87%/year), with majority of infections (65.0%) occurring within 1 year. Incidence of endocarditis declined in recent years. The most common organisms were Staphylococcus (22.0%), Streptococcus (20.0%), and Enterococcus (15.5%). Important predictors for endocarditis were younger age at TAVR, male sex, prior endocarditis, end-stage renal disease, repeat TAVR procedures, liver and lung disease, and post-TAVR acute kidney injury. Thirty-day and 1-year mortality were 18.5% and 45.6%, respectively. After adjusting for comorbidities and procedural complications, endocarditis after TAVR was associated with 3-fold higher risk of mortality (44.9 vs. 16.2 deaths per 100 person-years; adjusted hazard ratio [aHR]: 2.94; 95% confidence interval [CI]: 2.77 to 3.12; p < 0.0001). End-stage renal disease (aHR: 2.12; 95% CI: 1.72 to 2.60), endocarditis complicated by cardiogenic shock (aHR: 2.50, 95% CI: 1.56 to 4.02), ischemic stroke (aHR: 1.56; 95% CI: 1.07 to 2.28), intracerebral hemorrhage (aHR: 1.67; 95% CI: 1.01 to 2.76), acute kidney injury (aHR: 1.44; 95% CI: 1.27 to 1.63), blood transfusion (aHR: 1.28; 95% CI: 1.09 to 1.50), staphylococcal (aHR: 1.71; 95% CI: 1.49 to 1.97), and fungal endocarditis (aHR: 1.72; 95% CI: 1.23 to 2.39) (p < 0.05 for all) portended higher mortality following endocarditis. CONCLUSIONS: The incidence of endocarditis after TAVR is low and declining. However, it is associated with poor prognosis with one-half the patients dying within 1 year.

Management of Aortic Stenosis in Patients With End-Stage Renal Disease on Hemodialysis.

BACKGROUND: Patients with end-stage renal disease on hemodialysis (ESRD-HD) and aortic stenosis have poor prognosis. The role of transcatheter aortic valve replacement (TAVR) in this high-risk population is debated. METHODS: We compared the outcomes among ESRD-HD Medicare beneficiaries who were managed with TAVR, surgical AVR (SAVR), or conservative management for aortic stenosis between 2015 and 2017, using overlap propensity score weighting analysis to control for differences in treatment assignment. The primary outcome was all-cause mortality and was compared between treatment groups as well as to age-sex matched mortality for ESRD-HD in the US population. Secondary outcomes included trend of heart failure hospitalizations. RESULTS: A total of 8107 ESRD-HD patients with aortic stenosis were included, 4130 (50%) underwent TAVR, 2565 (31.6%) underwent SAVR, and 1412 (17.4%) were managed conservatively. TAVR patients had more comorbidities and higher frailty compared with the other 2 groups. Thirty-day mortality was lower with TAVR compared with SAVR (4.6% versus 12.8%, P<0.01). After a median follow-up of 465 days (interquartile range, 261-759), on overlap propensity score weighting analysis, there was no difference in mortality between TAVR and SAVR (adjusted hazard ratio, 1.02 [95% CI, 0.91-1.15], P=0.7), and mortality was lower with TAVR compared with conservative management (adjusted hazard ratio, 0.53 [95% CI, 0.47-0.60], P<0.001). Standardized mortality ratios with TAVR, SAVR, and conservative management compared with age-sex matched ESRD-HD US population were 1.24, 1.27, and 1.83, respectively. The rate of heart failure admissions declined after TAVR (incidence rate ratio, 0.55 [95% CI, 0.48-0.62], P<0.001) and SAVR (incidence rate ratio, 0.76 [95% CI, 0.65-0.88], P<0.001). CONCLUSIONS: In ESRD-HD patients with aortic stenosis, mortality was lower in the short-term with TAVR compared with SAVR but comparable in the mid-term. AVR is associated with an improvement in survival and reduction in heart failure hospitalizations compared with conservative management.

Incidence and Outcomes of Acute Coronary Syndrome After Transcatheter Aortic Valve Replacement.

OBJECTIVES: This study sought to address a knowledge gap by examining the incidence, timing, and predictors of acute coronary syndrome (ACS) after transcatheter aortic valve replacement (TAVR) in Medicare beneficiaries. BACKGROUND: Evidence about incidence and outcomes of ACS after TAVR is scarce. METHODS: We identified Medicare patients who underwent TAVR from 2012 to 2017 and were admitted with ACS during follow-up. We compared outcomes based on the type of ACS: ST-segment elevation myocardial infarction (STEMI), non-STEMI (NSTEMI), and unstable angina. In patients with non-ST-segment elevation ACS, we compared outcomes based on the treatment strategy (invasive vs. conservative) using inverse probability weighting analysis. RESULTS: Out of 142,845 patients with TAVR, 6,741 patients (4.7%) were admitted with ACS after a median time of 297 days (interquartile range: 85 to 662 days), with 48% of admissions occurring within 6 months. The most common presentation was NSTEMI. Predictors of ACS were history of coronary artery disease, prior revascularization, diabetes, valve-in-TAVR, and acute kidney injury. STEMI was associated with higher 30-day and 1-year mortality compared with NSTEMI (31.4% vs. 15.5% and 51.2% vs. 41.3%, respectively; p < 0.01). Overall, 30.3% of patients with non-ST-segment elevation ACS were treated with invasive approach. On inverse probability weighting analysis, invasive approach was associated with lower adjusted long-term mortality (adjusted hazard ratio: 0.69; 95% confidence interval: 0.66 to 0.73; p < 0.01) and higher risk of repeat revascularization (adjusted hazard ratio: 1.29; 95% confidence interval: 1.16 to 1.43; p < 0.001). CONCLUSIONS: After TAVR, ACS is infrequent (<5%), and the most common presentation is NSTEMI. Occurrence of STEMI after TAVR is associated with a high mortality with nearly one-third of patients dying within 30 days. Optimization of care is needed for post-TAVR ACS patients and if feasible, invasive approach should be considered in these high-risk patients.

Intracranial Atherosclerosis: A Disease of Functional, not Anatomic Stenosis? How Trans-Stenotic Pressure Gradients Can Help Guide Treatment.

BACKGROUND: Most trials have assessed intracranial atherosclerotic disease (ICAD) severity based on angiographic stenosis. However, anatomic stenosis might not accurately identify the actual state of functional post-stenotic flow limitation. OBJECTIVE: To investigate whether angiographic stenosis correlates with physiologic distal flow limitation, measured as trans-stenotic pressure gradients, in ICAD patients. METHODS: In patients referred for endovascular treatment of anterior circulation symptomatic ICAD who failed maximal medical therapy (MMT) per SAMMPRIS (Stenting versus Aggressive Medical Therapy for Intracranial Arterial Stenosis) criteria, angiographic luminal diameters and percentages of stenosis were correlated with trans-stenotic pressure gradients, calculated as distal/proximal pressure ratios (DPPR) and proximal minus distal pressure gradients (PDPG), by way of Spearman correlation coefficients. RESULTS: Nine patients (3 men, 6 women) were evaluated. Atherosclerotic lesions' locations included internal carotid artery in 5 subjects (2 cavernous, 3 supraclinoid) and proximal middle cerebral artery (M1) in 4 patients. Mean percentage of stenosis was 80 ± 8% (range 75%-94%). Minimal lumen diameter at the most stenotic ICAD site ranged from 0.2 to 0.9 mm (0.59 ± 0.41 mm). DPPR ranged from 0.38 to 0.63 (0.56 ± 0.14). PDPG ranged from 35 to 57 mm Hg (50 ± 8 mm Hg). Spearman coefficients showed no correlation between DPPR or PDPG and angiographic minimal luminal diameters or percentages of stenosis. There were no procedural complications related to trans-stenotic pressure measurements. CONCLUSION: Angiographic stenosis does not reflect the physiologic severity of distal flow limitation in patients with ICAD. Hemodynamic assessment using trans-stenotic pressure ratios and gradients may serve as a more reliable predictive biomarker for MMT failure and response to revascularization.

Temporal Trends and Clinical Outcomes of Transcatheter Aortic Valve Replacement in Nonagenarians.

Background Contemporary outcomes of transcatheter aortic valve replacement (TAVR) in nonagenarians are unknown. Methods and Results We identified 13 544 nonagenarians (aged 90-100 years) who underwent TAVR between 2012 and 2016 using Medicare claims. Generalized estimating equations were used to study the change in short-term outcomes among nonagenarians over time. We compared outcomes between nonagenarians and non-nonagenarians undergoing TAVR in 2016. A mixed-effect multivariable logistic regression was performed to determine predictors of 30-day mortality in nonagenarians in 2016. A center was defined as a high-volume center if it performed ≥100 TAVR procedures per year. After adjusting for changes in patients' characteristics, risk-adjusted 30-day mortality declined in nonagenarians from 9.8% in 2012 to 4.4% in 2016 (P<0.001), whereas mortality for patients <90 years decreased from 6.4% to 3.5%. In 2016, 35 712 TAVR procedures were performed, of which 12.7% were in nonagenarians. Overall, in-hospital mortality in 2016 was higher in nonagenarians compared with younger patients (2.4% versus 1.7%, P<0.05) but did not differ in analysis limited to high-volume centers (2.2% versus 1.7%; odds ratio: 1.33; 95% CI, 0.97-1.81; P=0.07). Important predictors of 30-day mortality in nonagenarians included in-hospital stroke (adjusted odds ratio [aOR]: 8.67; 95% CI, 5.03-15.00), acute kidney injury (aOR: 4.11; 95% CI, 2.90-5.83), blood transfusion (aOR: 2.66; 95% CI, 1.81-3.90), respiratory complications (aOR: 2.96; 95% CI, 1.52-5.76), heart failure (aOR: 1.86; 95% CI, 1.04-3.34), coagulopathy (aOR: 1.59; 95% CI, 1.12-2.26; P<0.05 for all). Conclusions Short-term outcomes after TAVR have improved in nonagenarians. Several procedural complications were associated with increased 30-day mortality among nonagenarians.

Bradycardia and Asystole in Patients Undergoing Symptomatic Chronically Occluded Internal Carotid Artery Recanalization.

BACKGROUND: Reports have emerged describing the successful endovascular recanalization of the chronically occluded internal carotid artery (COICA). The impact this restoration of flow has on the sensitive carotid sinus baroreceptors has not been previously described. In this manuscript, we present the largest COICA surgical series to date, with a specific focus on perioperative heart rate abnormalities. METHODS: Patient demographics were obtained, and the COICAs were radiographically classified based on the anatomic distribution of the stenosis and collateral flow. Thirty-six patients had a total of 37 COICA revascularization procedures. RESULTS: A total of 23 patients had intraprocedural bradycardia during balloon angioplasty. Three patients went into transient asystole during the procedure, and 2 of these patients had symptomatic bradycardia with ischemic cerebral changes, 1 of which required permanent pacemaking. All other patients had immediate resolution of their bradycardia, asystole, and neurologic symptoms immediately following balloon deflation and pharmaceutical management. There was a statistically significant difference in the observed proportion of bradycardic patients among COICA classifications (P = 0.014). There was no statistically significant difference in mean age between patients with bradycardia and those without (aged 63.36 vs. 67.71 years, P = 0.2265). CONCLUSIONS: Bradycardia associated with angioplasty of the carotid bulb was observed in the majority of patients receiving COICA revascularization. A small percentage of these patients were symptomatic. Our results suggest that carotid sinus baroreceptors remain active while residing in a complete arterial occlusion, and close monitoring is necessary during balloon angioplasty of the proximal COICA.

Transcatheter Repair of Anterior Mitral Leaflet Perforation: Deploy, Retrieve, Redeploy.

We describe a case of anterior mitral leaflet perforation successfully treated with the Amplatzer Cribriform device, with resultant hemolytic anemia. The device was retrieved, and perforation occluded with the GORE CARDIOFORM device with resolution of hemolysis. (Level of Difficulty: Advanced.).

Endovascular Treatment of Ruptured Vertebrobasilar Dissecting Aneurysms Using Flow Diversion Embolization Devices: Single-Institution Experience.

OBJECTIVE: Treatment of ruptured posterior circulation dissecting aneurysms is technically challenging with potentially high morbidity and mortality. We sought to assess the safety and feasibility of using a flow-diversion device (FDD) and a specific acute antiplatelet aggregation protocol in the management of ruptured dissecting aneurysms. METHODS: Subjects with ruptured dissecting aneurysms treated during a 3-year period were retrospectively identified from a prospective registry. Intraoperative complications, morbidity, and mortality were recorded. Tirofiban maintenance infusion without bolus was administered intravenously immediately after deployment of the FDD, and almost all patients were loaded with dual antiplatelet (aspirin and clopidogrel) post procedure. Clinical follow-up evaluation and modified Rankin Scale were assessed. RESULTS: Nine subjects with ruptured posterior circulation dissecting aneurysms were treated with an FDD: 5 vertebral artery, 2 basilar artery, and 2 posterior inferior cerebellar artery aneurysms. Average World Federation of Neurosurgical Societies score was 2 (range 1-5). Seven patients had external ventricular drain placed acutely for hydrocephalus. Eight patients received tirofiban infusion without bolus after FDD. No intraoperative complications occurred. Two subjects developed asymptomatic intraparenchymal hemorrhage found on surveillance noncontrast computed tomography. One subject suffered a major intraparenchymal hemorrhage and died a few days post intervention after additional anticoagulation was started for a left ventricular assist device. Follow-up modified Rankin Scale within 12 months was 0 in 3 subjects, 1 in 3 subjects, 2 in 1 subject, and 4 in 1. CONCLUSIONS: Treatment of dissecting posterior circulation aneurysms with FDDs is feasible and a potential alternative to deconstructive techniques.

Hybrid Retrograde-Antegrade Recanalization of Acute Basilar Artery Occlusion.

Acute basilar artery (BA) occlusion has a very poor prognosis. Recanalization can be challenged by bilateral vertebral artery (VA) occlusions, arterial dissection, or advanced atherosclerotic disease. We describe a case in whom the BA was accessed and recanalized through a retrograde-antegrade approach from the anterior circulation using a large posterior communicating artery (PCOM). Once the BA had been crossed retrogradely through the PCOM, another microcatheter was advanced antegradely through the VA into the BA and right posterior cerebral artery using the "buddy-wire" technique. In this way the BA was recanalized and reconstructed with stents. This technical note demonstrates a new approach to BA treatment when the antegrade access is hampered by advanced VA/BA disease or dissection.

Incidence of cerebral ischemic events after discontinuation of clopidogrel in patients with intracranial aneurysms treated with stent-assisted techniques.

OBJECT: The optimal antiplatelet medication protocol for prevention of thrombotic complications after stent-assisted coil embolization of cerebral aneurysms is unclear. Early cessation of antiplatelet agents may be associated with an increased risk of cerebral ischemic events. In this study, the authors assess the incidence of stroke or transient ischemic attack (TIA) following discontinuation of a 6-week course of clopidogrel in patients with cerebral aneurysms treated with stent-assisted techniques. METHODS: A retrospective review was conducted in all patients with cerebral aneurysms undergoing stent-assisted coil embolization or stent-in-stent flow diversion at the University of Iowa during a 24-month period. The antiplatelet protocol was 81 mg aspirin and 75 mg clopidogrel daily for 6 weeks, followed by 325 mg aspirin daily indefinitely. The incidence of stroke or TIA was determined by a retrospective review of medical records generated during a 3-month period following discontinuation of clopidogrel. RESULTS: A total of 154 patients underwent aneurysm treatment with stent techniques during this interval. Documentation of neurological follow-up 3 months after discontinuation of a 6-week clopidogrel treatment was available in 121 (78.6%) of 154 patients. Of these 121 patients, 114 were treated with stent-assisted coil embolization and 7 with stent-in-stent flow diversion. Six patients (5%) suffered an ischemic event after cessation of clopidogrel, with 2 events occurring within the first 2 weeks. Specifically, the rate of ischemic events was 5 (4.3%) of 114 in the "stent-coil" treatment group and 1 (14.3%) of 7 in the stent-in-stent group. Treatment had been performed in the setting of a subarachnoid hemorrhage in 1 patient. Atypical aneurysm features and technical factors predisposing to thrombotic events were found in all but one of these patients. Similarly, cardiovascular risk factors were present in 5 of the 6 patients in whom ischemic events developed after clopidogrel discontinuation. CONCLUSIONS: Clopidogrel discontinuation is associated with a 5% risk of ischemic events in patients treated with stent techniques. Any stroke related to clopidogrel discontinuation is avoidable, and longer treatment is therefore clearly necessary. Patients with cardiovascular risk factors, high-risk aneurysm features, and those undergoing stent-in-stent flow diversion might benefit the most from longer clopidogrel therapy.

Anterior-to-posterior circulation approach for mechanical thrombectomy of an acutely occluded basilar artery using the penumbra aspiration system.

OBJECTIVE: Prompt access to arterial occlusion is the key to successful endovascular revascularization in acute stroke. We present the first reported case utilizing anterior-to-posterior circulation approach for a successful mechanical thrombectomy and chemical thrombolysis of an acute basilar artery (BA) occlusion using the Penumbra Aspiration System. METHODS: A 39-year-old man with known left vertebral artery (VA) occlusion presented with a rapid progression of top of the basilar syndrome, resulting in a comatose status with flaccid motor exam and no corneal reflex. Navigation of a guide catheter into the right VA was unsuccessful because of an acute angle created by the previously placed right VA ostial stent that herniated into the subclavian artery. Left internal carotid artery-selective angiography revealed a prominent left posterior communicating artery. A Penumbra 026 reperfusion catheter was advanced into the thrombosed BA via the left internal carotid artery, the posterior communicating artery, and the P1 segment. Mechanical thrombectomy and chemical thrombolysis were successfully performed. RESULTS: TIMI-3 in the BA and TIMI-2 flows in posterior cerebral arteries were restored 8 hours 16 minutes after symptom onset. The patient had recovered full strength in all four extremities at 10 hours after the onset and had a National Institutes of Health Stroke Scale score of 2 at discharge. CONCLUSION: In patients with unfavorable VA anatomy, anterior-to-posterior thrombectomy of the BA can be successfully achieved using the Penumbra catheter via an anatomically suitable posterior communicating artery.

Risk of ventriculostomy-related hemorrhage in patients with acutely ruptured aneurysms treated using stent-assisted coiling.

OBJECT: Intracranial stenting has improved the ability to treat wide-neck aneurysms via endovascular techniques. However, stent placement necessitates the use of antiplatelet agents, and the latter may complicate the treatment of patients with acutely ruptured aneurysms who demonstrate hydrocephalus and require ventriculostomy. Antiplatelet agents in this setting could increase the incidence of ventriculostomy-related hemorrhagic complications, but there are insufficient data in the medical literature to quantify this potential risk. The aim of this study was to directly quantify the risk of ventriculostomy-related hemorrhage in patients with acute aneurysmal subarachnoid hemorrhage treated with stent-assisted coiling. METHODS: The authors retrospectively identified 131 patients who underwent endovascular treatment for an acutely ruptured aneurysm as well as ventriculostomy or ventriculoperitoneal (VP) shunt placement. The rate of hemorrhagic complications associated with ventriculostomy or VP shunt insertion was compared between patients who underwent coiling without a stent (Group 1) and those who underwent stent-assisted coiling and dual antiplatelet therapy (Group 2). RESULTS: One hundred nine ventriculostomies or VP shunt placement procedures were performed in 91 patients in Group 1, and 50 procedures were undertaken in 40 patients in Group 2. The rates of radiographic hemorrhage and symptomatic hemorrhage were significantly higher in Group 2 (32% vs 14.7%, p = 0.02; and 8% vs 0.9%, p = 0.03, respectively). On multivariate analyses, Group 2 had 3.42 times the odds of a radiographic hemorrhage (95% CI 1.46-8.04, p = 0.0048) after adjusting for antiplatelet use prior to admission. CONCLUSIONS: The application of dual antiplatelet therapy in stent-assisted coiling of acutely ruptured aneurysms is associated with an increase in the risk of hemorrhagic complications following ventriculostomy or VP shunt placement, as compared with its use in a coiling procedure without a stent.

Coronary arteries: imaging, reconstruction, and fluid dynamic analysis.

Atherosclerosis is the underlying cause of most cardiovascular-related deaths in industrialized nations. Determining the etiology of atherosclerosis and detecting lesions in the early stages of the disease for possible pharmacological or mechanical intervention have been challenges facing cardiovascular researchers. In addition to genetic and environmental factors, the formation and growth of atheroma have been linked to the complex fluid dynamics and mass transport in these arterial segments. This article reviews the current state of affairs in imaging modalities and image processing techniques that allow the visualization and morphologically realistic reconstruction of coronary arterial geometry to aid in the diagnosis and treatment of coronary artery disease (CAD). In addition, studies pertaining to our current understanding of the complex flow dynamics in the coronary arteries and the relationship between fluid-induced stresses on the initiation and growth of the atherosclerotic lesions are also reviewed. The article concludes with a brief discussion on possible future directions of research that will advance our knowledge of this challenging problem.

Plaque development, vessel curvature, and wall shear stress in coronary arteries assessed by X-ray angiography and intravascular ultrasound.

The relationships among vascular geometry, hemodynamics, and plaque development in the coronary arteries are complex and not yet well understood. This paper reports a methodology for the quantitative analysis of in vivo coronary morphology and hemodynamics, with particular emphasis placed on the critical issues of image segmentation and the automated classification of disease severity. We were motivated by the observation that plaque more often developed at the inner curvature of a vessel, presumably due to the relatively lower wall shear stress at these locations. The presented studies are based on our validated methodology for the three-dimensional fusion of intravascular ultrasound (IVUS) and X-ray angiography, introducing a novel approach for IVUS segmentation that incorporates a robust, knowledge-based cost function and a fully optimal, three-dimensional segmentation algorithm. Our first study shows that circumferential plaque distribution depends on local vessel curvature in the majority of vessels. The second study analyzes the correlation between plaque distribution and wall shear stress in a set of 48 in vivo vessel segments. The results were conclusive for both studies, with a stronger correlation of circumferential plaque thickness with local curvature than with wall shear stress. The inverse relationship between local wall shear stress and plaque thickness was significantly more pronounced (p<0.025) in vessel cross sections exhibiting compensatory enlargement (positive remodeling) without luminal narrowing than when the full spectrum of disease severity was considered. The inverse relationship was no longer observed in vessels where less than 35% of vessel cross sections remained without luminal narrowing. The findings of this study confirm, in vivo, the hypothesis that relatively lower wall shear stress is associated with early plaque development.

Remodeling characteristics of minimally diseased coronary arteries are consistent along the length of the artery.

Using a method that creates anatomically correct, 3-dimensional arterial reconstructions, 55 minimally diseased coronary arteries from 40 patients were studied. Homogenous remodeling characteristics along the entire length of the artery were observed in 48 arteries (87%). In the aggregate, arteries exhibited compensatory expansive remodeling. Individually, the full spectrum of compensatory expansive remodeling (60%), excessive expansive remodeling (21%), and constrictive remodeling (19%) was observed across arteries. Each artery was consistent in its remodeling characteristics from proximal to distal portions of the artery, and the remodeling pattern of each artery was independent within the same patient.

Effects of vessel geometry and catheter position on dose delivery in intracoronary brachytherapy.

In-stent restenosis is commonly observed in coronary arteries after intervention. Intravascular brachytherapy has been found effective in reducing the recurrence of restenosis after stent placement. Conventional dosing models for brachytherapy with beta (beta) radiation neglect vessel geometry as well as the position of the delivery catheter. This paper demonstrates in computer simulations on phantoms and on in vivo patient data that the estimated dose distribution varies substantially in curved vessels. In simulated phantoms of 50-mm length with a shape corresponding to a 60 degrees - 180 degrees segment of a respectively sized torus, the average dose in 2-mm depth was decreased by 2.70%-7.48% at the outer curvature and increased by 2.95%-9.70% at the inner curvature as compared with a straight phantom. In vivo data were represented in a geometrically correct three-dimensional model that was derived by fusion of intravascular ultrasound (IVUS) and biplane angiography. These data were compared with a simplified tubular model reflecting common assumptions of conventional dosing schemes. The simplified model yielded significantly lower estimates of the delivered radiation and the dose variability as compared with a geometrically correct model (p < 0.001). The estimated dose in ten vessel segments of eight patients was on average 8.76% lower at the lumen/plaque and 6.52% lower at the media/adventitia interfaces (simplified tubular model relative to geometrically correct model). The differences in dose estimates between the two models were significantly higher in the right coronary artery as compared with the left coronary artery (p < 0.001).