Infestation of urban populations of the Northern white-breasted hedgehog, Erinaceus roumanicus, by Ixodes spp. ticks in Poland.

Infestation by the nest-dwelling Ixodes hexagonus Leach and the exophilic Ixodes ricinus (Linnaeus) (Ixodida: Ixodidae) on the Northern white-breasted hedgehog, Erinaceus roumanicus (Erinaceomorpha: Erinaceidae), was investigated during a 4-year study in residential areas of the city of Poznan, west-central Poland. Of 341 hedgehogs, 303 (88.9%) hosted 10 061 Ixodes spp. ticks encompassing all parasitic life stages (larvae, nymphs, females). Ixodes hexagonus accounted for 73% and I. ricinus for 27% of the collected ticks. Male hedgehogs carried significantly higher tick burdens than females. Analyses of seasonal prevalence and abundance of I. hexagonus revealed relatively stable levels of infestation of all parasitic stages, with a modest summer peak in tick abundance noted only on male hosts. By contrast, I. ricinus females and nymphs peaked in spring and declined steadily thereafter in summer and autumn, whereas the less abundant larvae peaked in summer. This is the first longterm study to evaluate the seasonal dynamics of both tick species on populations of wild hedgehogs inhabiting urban residential areas.

Opportunities for further changes to the Medicare Benefits Schedule to support Aboriginal Community Controlled Health Organisations.

The Australian Government responded promptly to the need for minimising patient-clinician contact in the primary care setting during COVID-19 by introducing new funding for telehealth services as part of the Medicare Benefits Schedule (MBS). Funding for both telephone and videoconferencing provided primary care organisations, including Aboriginal Community Controlled Health Organisations (ACCHOs), with the ability to continue meeting the healthcare needs of their Communities, particularly given that Aboriginal and Torres Strait Islander Peoples were identified as susceptible to COVID-19. This perspective considers the need for proactive changes to the MBS to support the delivery of culturally appropriate primary healthcare services, including by mobile clinics, to Aboriginal and Torres Strait Islander Peoples by ACCHOs beyond the COVID-19 pandemic.

Limb salvage despite extensive tissue loss. Free tissue transfer combined with distal revascularization.

Extensive lower-extremity tissue loss may preclude limb salvage despite successful arterial reconstruction. We attempted to avoid limb loss in such patients by combining arterial bypass with microvascular free tissue transfer. Fourteen patient (12 diabetic), 33 to 74 years of age, presented with extensive tissue loss in 15 lower extremities, exposing bone or tendon on the heel, ankle, lower part of the leg, or hindfoot. Mean ulcer size was 5 X 8 cm. Four patients had had previous contralateral below-knee amputations. Femorodistal (seven), popliteal-distal (three), or femoropopliteal (four) bypass, or tibial angioplasty (one), was performed to provide sufficient inflow for free tissue transfer. Serratus anterior, scapular, latissimus dorsi, rectus abdominis, gracilis, ulnar, or temporalis free flaps were used. One free flap failed due to venous thrombosis and was corrected with a second flap. Limb salvage was achieved in 14 (93%) of 15 limbs during a mean follow-up of 24 months. The single amputation occurred due to severe foot ischemia in a patient whose femorodistal bypass remained patent only to the viable free flap. The remaining 13 patients (14 limbs) became ambulatory, including those with free flaps to weight-bearing regions.

Cost-effectiveness of intra-arterial thrombolytic therapy.

We reviewed the clinical course of 23 patients who received 24 intra-arterial infusions of either streptokinase or urokinase to treat 14 arteries and ten arterial grafts that were occluded due to primary thrombosis (22) or artery-artery embolism (two). Time from symptom onset to treatment was one to 28 days (mean, 11 days). Five infusions (21%) were completely successful since symptoms were eliminated without subsequent operation. Seven infusions (29%) were partially successful since thrombolysis aided, limited, or postponed subsequent surgery. Six infusions (25%) were failures since thrombolysis or clinical improvement did not occur and surgery was required. Six infusions (25%) were associated with thrombolytic complications that required urgent operation (less severe complications occurred in an additional 17% of cases [4/24]). Of the 19 patients without complete success after thrombolytic therapy, 16 underwent surgery during the same admission, two were not operable due to distal disease, and one declined operation. Of the 16 operations, 15 (94%) were successful in restoring graft or artery patency and achieving limb salvage, whereas one failed. In the 12 patients with failure or major complications of thrombolytic treatment, all had successful surgical outcome without morbidity. The actual mean cost of thrombolytic treatment was $8200 per patient and was comparable with the actual mean cost of subsequent surgical treatment in the 16 patients who required operation ($8900 per patient). The effective cost of thrombolytic and surgical treatment was calculated by dividing the actual costs by the proportion of successful cases. The effective cost of thrombolytic therapy per complete success was $39,200 and per complete or partial success was $16,500. This was significantly more than the effective cost of $9400 per complete success of surgical therapy.

Preoperative evaluation of the right internal thoracic artery for coronary surgery.

In general, the right internal thoracic artery (ITA) is used less frequently as a graft than the left ITA in coronary artery bypass grafting. To determine whether there is an anatomic or hemodynamic rationale for the underuse of the right ITA, noninvasive measurements of right and left ITAs were performed in 171 patients before the bypass procedure. Transthoracic visualization of both vessels was accomplished using a color-flow duplex scanner (5.0-MHz probe) through the third intercostal space. The diameter (in millimeters), peak systolic velocity (in centimeters per second), and end-diastolic velocity (in centimeters per second) were measured in all but 2 patients. The mean right ITA diameter was 2.7 +/- 0.6 mm, the mean peak systolic velocity was 100 +/- 29 cm/s, and the mean end-diastolic velocity was 6 +/- 5 cm/s. Diameter and flow velocity measurements for the right and left ITA were similar in all patients (p = not significant). The measured values for both sites were independent of age and sex, or the presence of hypertension or diabetes mellitus (p = not significant). We conclude that no morphologic or physiologic differences exist between the right and left ITAs. The findings from this study indicate that color-flow duplex ultrasound imaging is a safe and reliable noninvasive technique in the preoperative assessment of the anatomic and functional characteristics of the right ITA before coronary artery bypass grafting.

Coding and billing issues in the vascular laboratory.

Noninvasive vascular testing grew from a need for a safe, accurate, and inexpensive alternative to contrast injection venography and arteriography. The ultrasound studies performed to evaluate vascular disease today meet all expectations for safety and accuracy, and cost thousands of dollars less than their contrast counterparts, yet few sectors in medicine have been challenged so regularly by the Health Care Financing Administration (HCFA). Tests performed on duplex ultrasound instruments have prevented innumerable arterial and venous injuries and episodes of renal failure caused by contrast injection. Despite those laudable accomplishments, the financing agencies continue to reduce payments, threaten inappropriate supervisory requirements, and belittle the overall importance of the examinations. This report reviews the last decade of payment issues involving the vascular laboratory, pointing out inequities and problems that threaten not the quantity, but the quality, of this technology. The discussion focuses on Medicare Part B payments because they represent the majority of payments for noninvasive studies across the United States. The topics include payment denials, supervision issues, and problems associated with the zero work pool. In addition, the method by which HCFA calculates relative value unit (RVU) payments for procedures is included.

Resource-Based Relative Value Scale (RBRVS), coding, and Medicare reimbursement.

Many changes occurred during 1996 in the Resource-Based Relative Value Scale that determines physician payment for services to Medicare beneficiaries in 1997. These issues include the 5-year review of physician work values, the Correct Coding Initiative, changes in the surgical Conversion Factor, and a new Medicare payment formula. Likewise, several more changes on the horizon in 1997 will dramatically impact the 1998 Medicare Fee Schedule, primarily the upcoming resource-based Practice Cost Relative Value Scale, and possible elimination of the separate surgical Conversion Factors. There are also several new Current Procedural Terminology codes that will receive Medicare payment in 1997 and 1998. This article summarizes these events and issues from a vascular surgical perspective.

Can duplex ultrasound replace arteriography in screening for mesenteric ischemia?

Duplex examination of the mesenteric vasculature is not a widely performed examination, but the published literature documents the ability of this test to accurately identify chronic atherosclerotic occlusive disease. The test is a recent addition to the armamentarium of noninvasive duplex technology, with studies of adequate size for statistical analysis appearing only since 1991. Two primary sets of diagnostic threshold values for significant stenoses of the superior mesenteric artery (SMA) and the celiac artery have been published and subsequently tested for accuracy. One of these recommends use of peak systolic velocity (PSV), whereas end diastolic velocity (EDV) was found to be most accurate in the other. Both sets of criteria identify overall accuracy of greater than 90% for identification of SMA stenosis, and greater than 80% for diagnosis of celiac stenosis. Identification of celiac disease may be aided by analysis of blood flow direction in the common hepatic artery. The finding of retrograde hepatic flow is virtually diagnostic of severe celiac stenosis or complete occlusion. Duplex also has been shown capable of identifying anatomic anomalies of the mesenteric vessel origins, a situation that occurs in approximately 20% of the population. Finally, mesenteric duplex has utility in a variety of less common abdominal visceral disorders, but statistical analysis of accuracy and adequate identification of quantitative velocity thresholds have not been performed. Skilled technologists who have access to appropriate training and equipment can master this test. There is little doubt that it can replace angiography as a screening tool in the setting of suspected chronic mesenteric ischemia.

Vascular surgery and the Resource-based Relative Value Scale five-year review.

PURPOSE: The first 5-year review of the Medicare Resource-based Relative Value Scale (RBRVS) work values (RVUs) began in 1995, and adjustments became effective January 1, 1997. This report summarizes the methods used by The Society for Vascular Surgery (SVS) and the International Society for Cardiovascular Surgery, North American Chapter, (ISCVS-NA) Joint Council Government Relations Committee (GRC) to evaluate vascular surgery work RVUs and the results that were achieved. METHODS: The GRC performed a work study to determine accurate skin-to-skin operative times for typical vascular and nonvascular operations. These were compared with the original Harvard/Hsiao time estimates and intraservice work per unit time (IWPUT) values that had been used to determine work RVUs. For most vascular procedures the current operative times were longer than the original Harvard estimates, resulting in calculated IWPUTs substantially less than the Harvard values. This lack of correspondence was not identified in the nonvascular procedures, where operating room times and IWPUT values were more consistent with Harvard data. These study results were then used to support compelling evidence arguments in a petition to the Health Care Financing Administration (HCFA) that identified vascular surgery as being undervalued in the RBRVS. Nine commonly performed vascular procedures were cited for review in the 5-year update, and five distinct work analysis methods were used to justify each recommended RVU increase. These techniques included a standardized survey from the American Medical Association (AMA)/Specialty Society Relative Value Update Committee (RUC), a work calculation using accurate intraservice times and appropriate IWPUT values, and an evaluation and management (E&M) building-block approach. RESULTS: The RUC met throughout 1995 to assess codes submitted for review, and recommendations were forwarded to HCFA. The Notice of Proposed Rule Making (NPRM), which contained HCFA's preliminary RVU determinations, was released in May 1996. RVU increases from 11.5% to 44.6% were proposed for the nine vascular services cited by the SVS/ISCVS-NA. Also included were two increases and two reductions in less-common vascular operations. Of far greater overall fiscal import, HCFA proposed substantial increases in the work RVU for all E&M except that performed within global surgical packages. The SVS/ISCVS and most other surgical societies appealed HCFA's proposal regarding E&M. The Final Rule for the 1997 Medicare Fee Schedule was published late in 1996. CONCLUSIONS: The Final Rule upheld the 11 vascular work value improvements and the E&M increases that excluded global service packages. Because most surgical E&M is performed within 10- or 90-day global periods, the E&M ruling will produce an estimated annual $2.5 billion shift from surgical to nonsurgical specialties. Because the overall fiscal impact of the 5-year review was mandated to be budget-neutral, HCFA imposed an 8.3% reduction in the work payment of every service in Part B of the Medicare program, primarily to compensate for the increased nonsurgical E&M payments. The net fiscal impact of the 5-year review for vascular surgery has been estimated at +0.5%.

Kinetics of vein graft hyperplasia: association with tangential stress.

Vein grafts become thicker as they adapt to arterial circulation, and in large measure this is the consequence of cellular hyperplasia. The kinetics of smooth muscle cell (SMC) and endothelial cell (EC) replication were evaluated in rabbit jugular vein segments transplanted into the carotid arterial circulation to define the role of cell proliferation in this process, and these data were correlated with dimensional changes in grafts from 1 hour to 24 weeks after implantation. At 1 hour most of the perianastomotic endothelium was denuded, as were occasional cells in the graft away from the anastomosis. EC replication (thymidine labeling index) in the center of the graft increased 400 times during the first week and produced an intact endothelial surface by 2 weeks. The EC thymidine index then fell progressively to quiescent pretransplant levels by the twelfth week. SMC replication was maximal at 1 week after grafting and returned to near quiescent levels at 12 and 24 weeks. Graft wall thickness and cross-sectional area reached a maximum at 12 weeks and then remained constant. Deoxyribonucleic acid content exhibited a thirty-five-fold increase in the first 4 weeks, then did not change. Likewise, SMC mass did not increase after 4 weeks. Further increase in cross-sectional wall area between 4 and 12 weeks was accounted for by accumulation of connective tissue. The final ratio of luminal radius to wall thickness decreased to a level equal to that of normal artery. Since blood pressure did not change over the period of the study, this observation supports a possible regulatory role for wall tangential stress in the modification of vein graft structure after transplantation into the arterial circulation.

Danazol and limb-threatening arterial thrombosis: two case reports.

Danazol is a synthetic androgenic steroid used clinically for the treatment of a wide variety of disorders. Although there is no extensive evidence that androgens are thrombogenic in humans, there are case reports of cerebral, coronary, and peripheral arterial thrombosis in young male athletes abusing anabolic-androgenic steroids. There are also two reported cases of arterial and venous thrombotic events attributed to danazol therapy. We report two additional cases of limb-threatening arterial thrombosis in patients undergoing danazol therapy, and suggest the possibility that danazol may be an independent risk factor for arterial thrombosis.

Atherosclerosis in rabbit vein grafts.

Human coronary saphenous vein bypass grafts develop atherosclerosis more readily than do grafts made of internal mammary artery. The reasons for this increased susceptibility, particularly in the presence of hyperlipidemia, are not known. In this study in rabbits, we investigated the possibility that the increased susceptibility might be attributed to increased smooth muscle proliferation and foam cell accumulation in vein grafts compared to native artery. Hypercholesterolemic and control rabbits underwent placement of jugular vein grafts in the carotid artery. Dietary cholesterol content was adjusted to maintain serum cholesterol levels of 200 to 600 mg/dl in the fat-fed rabbits. The vein graft intimal thickness in hypercholesterolemic rabbits was greater than in normolipemic rabbits at 3 and 6 months after implant. The increased thickness in the hypercholesterolemic group was largely accounted for by an accumulation of lipid-laden macrophages. Medial thicknesses increased during the first month, remained constant at later times, and were similar in control and hypercholesterolemic animals. In both groups, endothelial and smooth muscle cell proliferation (thymidine labeling) increased immediately after graft implantation and declined at 3 and 6 months. No incremental mitogenic stimulus could be attributed to the hypercholesterolemia. In immunohistochemical preparations, the large foam cells were noted to be macrophages, and the intimal proliferating cells, to be smooth muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Vein adaptation to the hemodynamic environment of infrainguinal grafts.

PURPOSE: Although arteries appear to remodel in response to changes in hemodynamic parameters such as shear stress, little is known about functioning human vein grafts. This study was designed to explore diameter changes in human saphenous vein grafts after infrainguinal bypass. METHODS: We used duplex ultrasonography to measure hemodynamic variables that might affect the diameter of 48 in situ saphenous vein grafts during the first year after infrainguinal arterial bypass. Volumetric flow rate, average velocity, peak systolic velocity, and vein diameter in the proximal and distal thirds of these grafts were each measured at 1 week and at 3, 6, and 12 months after operation. Veins were divided into three groups based on initial size (1 week after bypass) in the below-knee segment: small, < 3.5 mm diameter; medium, 3.5 to 4 mm diameter; and large, > 4 mm diameter. RESULTS: Distal vein diameters at 1 week for small, medium, and large grafts were 2.9 +/- 0.1, 3.7 +/- 0.1, and 4.3 +/- 0.1 mm, respectively (p < 0.001), but by 12 months these diameters were 3.6 +/- 0.2, 3.8 +/- 0.2, and 3.9 +/- 0.2 mm, respectively (p = 0.54). Large veins decreased in diameter, whereas small veins increased in diameter, as confirmed by linear regression of percent change in diameter versus initial vein graft diameter (r = -0.62, p < 0.001). Volumetric flow rate, peak systolic velocity, and shear stress also tended to approach uniform values over time. Of the hemodynamic variables studied, the best predictor of diameter change was shear stress (linear regression of percent change in diameter vs shear stress, r = 0.67, p < 0.001). Veins with a diameter increase greater than 10% over time had significantly higher initial shear stress than veins with a diameter decrease greater than 10% over time (28.6 +/- 3.8 vs 13.1 +/- 1.8 dynes/cm2, p < 0.01), whereas initial volumetric flow rates in these two groups were similar (135 +/- 23 vs 130 +/- 15 ml/min). CONCLUSIONS: Infrainguinal in situ vein graft diameter, volume flow rate, peak systolic velocity, and shear stress all tend to stabilize at uniform values regardless of the initial vein graft diameter. Of the hemodynamic variables studied, shear stress is most strongly associated with the change in diameter over time. Thus human saphenous vein appears to be capable of adapting to its hemodynamic environment after arterial grafting by modulating diameter to normalize shear stress.

Predicting outcome of angioplasty and selective stenting of multisegment iliac artery occlusive disease.

BACKGROUND: Patients who require angioplasty and stenting of multiple iliac arterial segments often require reintervention to maintain long-term patency. Morphologic predictors and causes of failure are unknown. The purpose of the current study was to define arteriographic predictors of angioplasty and selective stent failure in the treatment of multisegment iliac occlusive disease. METHODS: All iliac segments (two common and two external) of 75 patients who underwent angioplasty and selective stent placement for multisegment iliac occlusive disease (>/= two segments) were scored through use of a modification of the Society of Cardiovascular and Interventional Radiology classification for iliac angioplasty (0 = no lesion; 4 = most severe). Total iliac score was calculated by summing scores from each segment. A separate external iliac score was calculated by adding only the external iliac scores. Arteriograms were reviewed initially and at the time of lesion recurrence and stratified by lesion location and previous intervention. RESULTS: The area of previous endovascular intervention was the site of recurrence in 75% of patients. New lesions, presumably a result of progressive atherosclerosis, occurred in 15% of patients, and lesions occurred in both new and previously treated iliac segments in 10% of patients. Only the external iliac score was an independent predictor of failed endovascular therapy despite reintervention. For patients with an external iliac score of 2 or less, the endovascular primary-assisted patency rates at 6, 12, and 24 months were 96%, 92%, and 89%, respectively. This was improved in comparison with the 90%, 63%, and 45% patency rates observed in patients with an external iliac score of 3 or more (P =.001). Patients with an external iliac score of 3 or more had a significantly lower incidence of hemodynamic and clinical improvement after intervention and a threefold higher need for surgical inflow procedures than patients with an external iliac score of 2 or less. CONCLUSIONS: Lesion formation after treatment of multisegment iliac occlusive disease typically occurs in areas of prior intervention. The extent of external iliac disease can be used to stratify patients with multisegment iliac occlusive disease who will likely respond to endovascular treatment with a durable result. Patients with extensive external iliac disease (score >/= 3) have poor results after angioplasty and selective stenting as applied in this study, even with endovascular reintervention. They are ideal subjects for prospective comparative studies of competing initial therapies, including stenting, endografting, and aortobifemoral bypass grafting.

Vascular laboratory cost analysis and the impact of the Resource-Based Relative Value Scale payment system.

PURPOSE: This study compares the actual cost of performing noninvasive laboratory studies with reimbursement under the previous Medicare Part B system and under current resource-based relative value scale (RBRVS) guidelines. METHODS: We calculated the cost to operate our own laboratory and estimated national costs for small- and large-model laboratories. Reimbursement under Medicare Part B was calculated for each Current Procedural Terminology code from average Medicare reimbursement allowances and national case volumes in 1990, which were obtained from the Health Care Financing Administration. All data were expressed as dollars per hour of study time to allow universal comparison of costs and reimbursement among tests that require differing lengths of time for completion. RESULTS: Technical costs for laboratory time ranged from $143 to $173 per study hour. The largest components of laboratory expenses were fixed costs, including personnel (37% to 46%), equipment (30% to 42%), and facilities (6% to 8%). Variable costs such as billing (9% to 10%) accounted for most of the remainder. More efficient allocation of equipment resulted in lower costs in large laboratories, whereas continued use of depreciated equipment resulted in lower costs in our own laboratory ($127/hr). CONCLUSIONS: We project that technical reimbursement under RBRVS will be $82/hr nationally and $80/hr locally, whereas global reimbursement (technical plus professional) will be $116/hr and $110/hr, respectively. On the basis of 1990 case volumes, the RBRVS system will decrease national global reimbursement by at least 35% compared with the previous Medicare Part B system. Under the new system, technical reimbursement will decrease by an estimated 27% nationally, whereas professional reimbursement will decrease by 52%. Revenue under RBRVS will not meet the cost to perform studies either nationally or locally. Technical reimbursement is 37% to 54% below actual technical costs, and even global reimbursement is 13% to 34% less than technical costs. Our analysis revealed that costs will exceed reimbursement despite maximization of operating efficiency. This analysis applies to outpatients only. A case mix including inpatients will further reduce reimbursement, because only the professional component is allowed. By setting reimbursement of vascular laboratories below actual costs, the new RBRVS system may ultimately reduce the availability of noninvasive vascular testing for elderly patients.

Differential response of arteries and vein grafts to blood flow reduction.

PURPOSE: This study was undertaken to evaluate the effect of blood flow on the dimensions and cellular composition of normal arteries and freshly placed vein grafts (VG). METHODS: Bilateral jugular vein interposition grafts were placed in the common carotid arteries of 12 New Zealand white rabbits, and blood flow was reduced on one side by external carotid artery ligation. Shear stress, tangential stress, vessel dimensions, and smooth muscle cell (SMC) proliferation of reduced-flow arteries and VG were compared with these measures in contralateral controls (CON). RESULTS: A sustained reduction in blood flow was documented at 4 weeks (13 +/- 4 ml/min reduced-flow vs 21 +/- 4 ml/min CON; p < 0.05). Reduced-flow carotid arteries had a smaller lumen radius and greater medial thickness compared with normal-flow arteries, but there was no difference in medial cross-sectional area or medial SMC volume and no differences in any intimal measurements. These changes resulted in normalization of shear stress (15.2 +/- 4.6 dynes/cm2 reduced-flow vs 13.6 +/- 2.5 dynes/cm2 CON; p = NS). All VG underwent a marked postimplantation hyperplasia in intima and media, but the major effect of flow reduction on VG dimensions occurred in the intima. Intimal thickness in reduced-flow VG was 60% greater than that in control VG (57 +/- 12 microns vs 35 +/- 5 microns; p = 0.05), and intimal area was 70% greater than that in controls (0.83 +/- 0.24 microns 2 vs 0.48 +/- 0.08 microns 2; p > 0.05). Smaller differences were found in medial thickness (74 +/- 4 microns reduced-flow vs 63 +/- 4 microns CON; p = 0.02) and medial area (1.03 +/- 0.36 microns 2 reduced-flow vs 0.84 +/- 0.22 microns 2 CON; p = 0.05). Intimal SMC volume in reduced-flow VG was 37% greater than that in control VG (p = 0.07). Tangential stress in VG equaled that in ipsilateral arteries, whereas shear stress in VG remained much lower than that in arteries. CONCLUSIONS: In this model, arteries and VG responded to flow reduction by wall thickening, but the mechanism differed. Arteries underwent medial remodeling, lumen caliber reduction, and shear stress normalization, whereas VG responded by an upward modulation of the proliferative response that follows graft placement. These data support a primary role for tangential stress and a secondary role for shear stress in determination of VG dimensions.

Psoas abscess following intravesical bacillus Calmette-Guerin for bladder cancer: a case report.

An 87-year-old man with an abdominal aortic aneurysm received intravesical bacillus Calmette-Guerin therapy for transitional cell carcinoma of the bladder. He presented 9 months later with a psoas abscess that mimicked a contained retroperitoneal abdominal aortic aneurysm rupture. The abscess cultures yielded Mycobacterium bovis. Recent transurethral resection and high voiding pressures after instillations of bacillus Calmette-Guerin may have led to distant dissemination of the drug.

Regional coronary perfusion and bioenergetics in experimental atherosclerosis.

The effects of experimental coronary atherosclerosis on myocardial high energy phosphates and regional coronary perfusion and oxygen delivery were studied. Hypercholesterolemic (HC) New Zealand white rabbits developed mild to moderate coronary vascular disease in 4 months when serum cholesterol levels were maintained at 1500--2000 mg/dl. Resting left ventricular levels of creatine phosphate, adenosine triphosphate (ATP), and the cellular energy charge were unaltered after 2 months of diet but were decreased after 4 and 6 months. Tissue lactate and the lactate/pyruvate ratio were increased after 4 months, suggesting mild tissue ischemia. The regional blood flow rate was measured in rabbits given pentobarbital after 6 months of diet using labeled microspheres, and the response to stress was tested after 5 minutes of hypoxic ventilation (5% O2/N2). The percentage of cardiac output to subendocardium (endo) and subepicardium (epi) in HC rabbits and that in control animals were similar at rest, but unlike that of control animals, the endo perfusion did not increase significantly in HC animals during hypoxic stress. Baseline regional left ventricular oxygen deliveries were similar between groups, but the baseline endo/epi oxygen delivery ratio was reduced in HC rabbits. In control rabbits hypoxia did not alter total O2 delivery, and the endo/epi oxygen delivery ratio was constant, whereas hypoxia in HC animals produced a decrease in total oxygen delivery and a further decrease in the endo/epi oxygen delivery ratio. Thus, moderate long-term coronary occlusive disease produced alterations in the distribution of coronary perfusion that are similar to those after acute partial occlusion, ie, selective reductions in blood flow and oxygen delivery to subendocardium. These results may relate to the pathogenesis of subendocardial infarction in man, which often occurs in the absence of complete coronary occlusion.