Biomedical subjects

J D Hilton

Publications and source records attributed to J D Hilton.

15 recordsLinked to original sources

PubMed2001

Initial experience with a low profile, high energy excimer laser catheter for heavily calcified coronary lesion debulking: parameters and results of first seven human case experiences.

BACKGROUND: Excimer laser coronary angioplasty (ELCA) has not been used in the setting of highly calcified, tight stenoses because the energies required to use existing catheters would lead to excessive heat damage and dissection. There are, however, cases that frequently benefit from debulking prior to percutaneous intervention. A new, small laser catheter capable of high energies and repetition was previously examined in vitro. This study describes the first in vivo use. PURPOSE: To determine the safety and feasibility of a new, low profile, high energy laser catheter for creating a pilot hole to facilitate coronary angioplasty and stenting in patients with heavily calcified and occluded coronary arteries where a balloon has either failed to pass or was predicted to perform poorly. These patients represent the first patients treated with this new catheter. METHODS: At a high volume center, seven consecutive patients with anatomy as summarized above were treated and studied with QCA and then followed for 30 days postprocedure for complications and Canadian Cardiovascular Society (CCS) angina class. RESULTS: The laser catheter crossed five out of seven lesions and partially penetrated the remaining lesions. The mean maximum luminal diameter (MLD) postlasing was 1.0 mm with Thrombolysis in Myocardial Infarction (TIMI) 3 flow. It was possible to easily balloon and stent after the pilot hole creation in all but one patient. TIMI 3 was achieved for the final result after adjunct therapy in all patients. All patients except one, who died at 3 months postprocedure of stroke, were improved by an average of two angina classes. No late procedural-related complications developed. CONCLUSIONS: The new, low profile laser catheter is easy to use and achieved good results in cases where a balloon either failed to pass or was predicted to give poor results. Further trials are warranted for this niche technology.

Aged↗

PubMed2000

Effects of 3 analgesic regimens on the perception of pain after removal of femoral artery sheaths.

BACKGROUND: Effective pain management after removal of femoral artery sheaths after percutaneous transluminal coronary angioplasty is highly individualized and requires frequent, accurate assessment and administration of analgesics as needed. OBJECTIVE: To determine which of 3 analgesic regimens is most effective in decreasing patients' perception of pain with the fewest side effects after removal of a femoral artery sheath. SAMPLE: 130 adult who had undergone percutaneous transluminal coronary angioplasty and were in an 8-bed cardiac short-stay unit in a 1400-bed acute care hospital. METHOD: Patients were randomized to receive either intravenous morphine, intravenous fentanyl, subcutaneous lidocaine around the sheath site, or an intravenous placebo before sheath removal. Rescue analgesia (intravenous fentanyl) was made available to all groups. Patients used a visual analog scale to assess pain within 10 minutes before, 1 minute after, and 20 minutes after sheath removal. Pain levels, frequency of side effects, and use of rescue analgesia were compared among groups. RESULTS: Age, sex, number of stents, and frequency of hematomas did not differ significantly among groups. Pain ratings, use of rescue analgesia, and side effects (nausea, vomiting, or vasovagal symptoms) were not significantly different among treatment groups. Ratings of pain were slightly higher immediately after sheath removal in all groups. CONCLUSION: For most patients, removal of femoral artery sheaths and manual compression for hemostasis are relatively pain-free. Pain scores among patients given analgesia with subcutaneous lidocaine, intravenous morphine, or intravenous fentanyl were not significantly different from pain scores among control patients.

Adult↗

PubMed1999

Improved clinical outcome after widespread use of coronary-artery stenting in Canada.

BACKGROUND: The introduction and refinement of coronary-artery stenting dramatically changed the practice of percutaneous coronary revascularization in the mid-1990s. We analyzed one-year follow-up data for all percutaneous coronary interventions performed in a large, unselected population in Canada to determine whether the use of coronary stenting has been associated with improved outcomes. METHODS: Prospectively collected data on all percutaneous coronary interventions performed on residents of British Columbia, Canada, between April 1994 and June 1997 were linked to province-wide health care data bases to provide the date of the following end points: subsequent target-vessel revascularization, myocardial infarction, and death. Baseline characteristics and procedural variables were identified and Kaplan-Meier survival curves were generated for 9594 procedures divided into seven groups, one for each sequential half-year period. RESULTS: The overall burden of coexisting illnesses remained stable throughout the study period. A large increase in the rate of coronary stenting (from 14.2 percent in the period from April to June 1994 to 58.7 percent in the period from January to June 1997) was associated with a significant reduction in the rate of adverse cardiac events at one year (from 28.8 percent to 22.8.percent; adjusted relative risk, 0.79; 95 percent confidence interval, 0.69 to 0.90; P<0.001). This reduction in adverse events was exclusively due to a large reduction in subsequent target-vessel revascularization (from 24.4 percent to 17.0 percent; adjusted relative risk, 0.72; 95 percent confidence interval, 0.62 to 0.83; P<0.001) without significant changes in the overall rates of myocardial infarction (5.4 percent, P=0.28) or death (3.9 percent, P=0.65). CONCLUSIONS: The need for target-vessel revascularization during one year of follow-up decreased after percutaneous coronary intervention during the mid-1990s. The reduction was coincident with the introduction and subsequent widespread use of coronary stenting.

Angioplasty, Balloon, Coronary↗

PubMed1997

Usefulness of coronary stenting for cardiogenic shock.

Coronary stenting was performed in 15 selected patients with cardiogenic shock, with favorable clinical and angiographic outcomes. This experience suggests that coronary stenting may play an important adjunctive role in the management of cardiogenic shock and may improve outcome beyond that achieved with balloon angioplasty alone.

Aged↗

PubMed1995

Femoral arterial sheath removal after PTCA: a cross-Canada survey.

A cross-sectional survey was conducted to examine current Canadian practices in the nursing and medical management of femoral arterial sheath removal (SR) after PTCA (percutaneous transluminal coronary angioplasty). The purposes of the study were to (a) investigate the roles of the nurses and physicians in SR, (b) assess the length of time arterial sheaths are left in place and patients kept on bedrest, and (c) describe the routine medical protocols used for pain and anticoagulation therapy. Of the 35 hospitals that perform PTCA in Canada, 30 responded to the survey (response rate of 86%). Nurses had primary responsibility for SR in 13% of the sites and shared responsibility with physicians for SR in a further 10% of the institutions. When nurses were trained to remove sheaths, they assumed responsibility for the adjunctive steps to establish hemostasis. One third of hospitals removed sheaths in 4 hours or less; approximately 75% of them removed sheaths in 6 hours or less after PTCA. Patients are kept on bedrest for 6 hours or less following hemostasis in half, and 8 hours or less at three-quarters of the hospitals. Post-PTCA and pre-SR anticoagulant monitoring was used in almost half of the sites. Premedication for SR varied from no premedication to combinations of three intravenous medications plus local anaesthetic. Survey results showed that in almost one quarter of the Canadian institutions where PTCA is performed, nurses play a role in SR. Results also showed that there is no uniformity in post-PTCA SR across Canada and that further research is needed to identify the optimum approach to managing this common cardiovascular procedure.

Angioplasty, Balloon, Coronary↗

PubMed1994

Patterns of practice analysis for acute myocardial infarction.

OBJECTIVE: To assess the level of use of acetylsalicylic acid (ASA), beta-blockers and thrombolytic therapy--proven efficacious therapies in the management of acute myocardial infarction (AMI)--in contemporary patients admitted with AMI, and to assess the role of contraindications and other patient-specific factors in the use or nonuse of these treatments. DESIGN: The demographics and treatment course of patients admitted with a diagnosis of AMI were reviewed. Specifically targeted therapies were ASA, beta-blockers and thrombolytic therapy. Rates of use were calculated as 'gross utilization' (overall use) and 'adjusted utilization' (accounting for late presentation to hospital, initially equivocal diagnosis or contraindications). SETTING: Tertiary care hospital in suburban Vancouver, British Columbia. PATIENTS: A total of 372 consecutive patients admitted to Royal Columbian Hospital between September 1, 1990 and September 1, 1991. INTERVENTIONS: None. MAIN RESULTS: Gross utilization of ASA, beta-blockers and thrombolytic therapy was 71, 31 and 21%, respectively. The adjusted utilization rates for early (6 h or less) treatment with ASA was 66%; with early beta-blockers, it was 18% and was 100% for thrombolytic therapy. Adjusted late (more than 6 h, to hospital discharge) use of ASA and beta-blockers was 84 and 57%, respectively. CONCLUSIONS: With the exception of thrombolytic therapy, proven efficacious medical therapies for AMI appear underused at the study hospital. Ongoing educational efforts and continuing patterns of practice analyses are needed.

Adrenergic beta-Antagonists↗

PubMed1993

Quantitative proton spectroscopy and histology of a canine brain tumor model.

Quantitative, single voxel proton nuclear magnetic resonance (NMR) spectroscopy and histological analysis was performed in eight dogs implanted with the transplantable canine glioma model of Wodinsky (Proc. Am. Assoc. Cancer Res. 10, 99 (1969)). Signals from choline, creatine, N-Acetyl Aspartate (NAA) and lactate were converted to molar concentration units and correlated with the quantitative analysis of histologically determined tissue types within the localized volume selected for NMR spectroscopy. In general, compared with normal brain, the lesions were associated with reductions in all metabolite concentrations, with the exception of lactate, which was increased. NAA and creatine decreases were most significantly correlated with the total lesion volume (P < 0.01), suggesting that these compounds are present in normal brain only. Changes in choline levels did not correlate strongly with any particular tissue type. Lactate was found to increase with increasing total lesion volume (P < 0.01), but not with increasing percent tumor, suggesting that it accumulates in abnormal tissue other than the tumor. The spectra reported were similar to those observed in human glioblastomas, with the exception that elevations of choline were not observed. The transplantable canine gliosarcoma system appears to be a suitable tumor model for evaluation by clinical radiological techniques such as magnetic resonance imaging (MRI) and proton NMR spectroscopy.

Animals↗

PubMed1984

Clinically unrecognized ventricular dysfunction in young diabetic patients.

Left ventricular function at rest and during supine bicycle exercise was assessed by gated radionuclide angiography in 20 diabetic patients and 18 normal control subjects without clinical evidence of heart disease. The diabetic patients were aged 21 to 44 years and all except one used insulin. No subject developed chest pain or electrocardiographic changes during exercise. Both groups had a similar rest and exercise heart rate and blood pressure, and both achieved similar work loads. The control group had an ejection fraction at rest of 65.4 +/- 6.2% (mean +/- SD) and only 1 of 18 showed a decrease with exercise; peak exercise ejection fraction averaged 77.1 +/- 7.8%. The diabetic group had a mean ejection fraction at rest of 63.7 +/- 6.5%, similar to that of the control group, but 7 of 20 showed a decrease during exercise; the exercise ejection fraction averaged 67.7 +/- 9.7%, significantly lower than that of the control group (p less than 0.01). The diabetic patients varied widely in ejection fraction response to exercise, ranging from an increase of 25% to a decrease of 21%. This response did not correlate with age, sex, duration of diabetes, smoking, retinopathy, exercise heart rate, blood pressure or rate-pressure product, work load attained or ejection fraction at rest. These data suggest that approximately one-third of patients with diabetes have subclinical left ventricular dysfunction without correlation to risk factors for atherosclerosis or other diabetic complications. Whether this is due to unrecognized coronary artery disease or primary myocardial disease remains unknown.

Adult↗

PubMed1984

Rewarming hypovolemia after aortocoronary bypass surgery.

Coronary bypass performed with moderate systemic hypothermia (25 degrees C) and cold-potassium cardioplegia was associated with a fall and subsequent rise in core (pulmonary arterial) temperature. Serial hemodynamic measurements during rewarming and recovery revealed a decrease in cardiac index (CI) without a decrease in the left atrial pressure (LAP) of 17 patients recovering from uneventful coronary bypass surgery. Nuclear ventriculograms performed during rewarming demonstrated a decrease in left ventricular end-diastolic volume index (EDVI, calculated from the thermodilution stroke index divided by the nuclear ejection fraction) without a change in LAP. Volume loading during both mild hypothermia (35 +/- 5[SD]degrees C) and normothermia revealed that myocardial performance (the relation between CI and EDVI) was unchanged, but diastolic compliance (the relation between LAP and EDVI) decreased with rewarming. LAP was a poor indicator of left ventricular preload (EDVI) during rewarming, and volume loading was required to maintain preload and prevent hypoperfusion.

Atrial Function↗

PubMed1983

Rest and exercise ventricular function in adults with congenital ventricular septal defects.

Rest and exercise right and left ventricular function were compared using equilibrium gated radionuclide angiography in 19 normal sedentary control subjects (mean age 28 years, range 22 to 34) and 34 patients with hemodynamically documented congenital ventricular septal defect (VSD) (mean age 27 years, range 20 to 40). The 34 patients with VSD were divided into 3 groups: those in Group 1 (17 patients) had pulmonary to systemic blood flow ratios of less than 2 to 1; those in Group 2 (12 patients) had prior surgical closure of VSD (mean interval from surgery 17 years, range 9 to 22), and those in Group 3 (5 patients) had Eisenmenger's complex. Gated radionuclide angiography was performed at rest and during each level of graded supine bicycle exercise to fatigue. Heart rate, blood pressure, maximal work load achieved, and right and left ventricular ejection fractions were assessed. The control subjects demonstrated an increase in both the left and right ventricular ejection fractions with exercise (0.70 +/- 0.07 to 0.79 +/- 0.05 and 0.46 +/- 0.06 to 0.57 +/- 0.04; p less than 0.001 for left and right ventricles, respectively). All study groups failed to demonstrate an increase in ejection fraction in either ventricle with exercise. Furthermore, resting left ventricular ejection fraction in Groups 2 and 3 was lower than that in the control subjects (0.59 +/- 0.09 and 0.54 +/- 0.06 versus 0.70 +/- 0.07; p less than 0.001) and resting right ventricular ejection fraction was lower in Group 3 versus control subjects (0.30 +/- 0.07 versus 0.46 +/- 0.06; p less than 0.001). Thus (1) left and right ventricular function on exercise were abnormal in patients with residual VSD as compared with control subjects; (2) rest and exercise left ventricular ejection fractions remained abnormal despite surgical closure of VSD in the remote past; (3) resting left and right ventricular function was abnormal in patients with Eisenmenger's complex; (4) lifelong volume overload may be detrimental to myocardial function.

Adult↗

PubMed1983

A comparison of volume loading and atrial pacing following aortocoronary bypass.

Although cold potassium cardioplegia provides adequate myocardial protection, transient hemodynamic and metabolic instability occasionally occurs after uncomplicated coronary bypass surgery. Two methods to increase cardiac output were compared 2 to 6 hours postoperatively in 24 patients recovering from elective coronary bypass operation. Volume loading increased cardiac index (CI) from 2.1 +/- 0.5 to 2.7 +/- 0.6 L/min/m2 by increasing left atrial pressure (LAP) from 8.6 +/- 3.6 to 13.0 +/- 4.1 mm Hg. Atrial pacing at a rate of 112 +/- 8 beats per minute increased CI from 2.4 +/- 0.5 to 2.7 +/- 0.8 L/min/m2 without a change in LAP. Ejection fraction by nuclear angiography did not change, but the calculated left ventricular end-diastolic volume index (stroke index/ejection fraction) increased with volume loading and decreased with atrial pacing--a decrease in diastolic compliance. Myocardial oxygen extraction did not change, but myocardial lactate extraction increased with volume loading and decreased with atrial pacing. Coronary sinus blood flow was measured in 5 patients and increased with both methods studied. Volume loading demonstrated that myocardial performance was normal and myocardial metabolism increased commensurate with the increase in work. Atrial pacing increased CI but resulted in anaerobic metabolism and a decrease in diastolic compliance. Volume loading rather than atrial pacing will improve CI without producing ischemia in the early postoperative period.

Adult↗

PubMed1983

Optimal postoperative volume loading.

Intravenous infusions are required to maintain ventricular preload after uneventful coronary bypass operation. During the early postoperative period, when myocardial metabolic recovery is incomplete, volume loading is intended to stabilize ventricular function and metabolism and to prevent progressive ischemic injury. This study attempts to define the optimal preload for both metabolism and performance. Thirty-seven patients recovering from elective coronary bypass operations and cold potassium cardioplegia underwent volume loading with whole plasma. The initial response (VLA) from a low left atrial pressure (LAP = 7.3 +/- 3.3 mm Hg) was compared with the subsequent response (VLB) from a higher filling pressure (LAP = 10.9 +/- 2.7 mm Hg). Both VLA and VLB produced a similar increase in cardiac index, stroke work index, and end-diastolic volume index (EDVI), and a decrease in ejection fraction (measured by nuclear angiography). Myocardial lactate extraction increased with VLA, but myocardial lactate production resulted with VLB. A careful analysis of these volume loading studies suggested that myocardial performance and compliance were not altered in the early postoperative period. The decrease in ejection fraction with volume loading may have resulted from a combination of increased wall tension and decreased inotropic stimulation. After uneventful coronary bypass surgery, an LAP between 5 and 12 mm Hg corresponded to an EDVI between 30 and 80 ml/m2 and produced adequate cardiac index, stroke work index, and lactate extraction. A lower or higher preload did not improve function and resulted in abnormal metabolism.

Coronary Artery Bypass↗

PubMed1983

Comparison of alternative cardioplegic techniques.

Cold potassium cardioplegia provides adequate protection for coronary bypass operations, but severe coronary stenoses limit cardioplegic delivery to ischemic regions. The traditional technique delivers cardioplegic solution into the aortic root during the performance of distal anastomoses. The proposed alternative technique constructs proximal as well as distal anastomoses during a prolonged cross-clamp period, but permits more uniform cooling. The two techniques were compared in a prospective concurrent trial of 45 patients undergoing elective coronary bypass grafting. The traditional technique was employed in 26 patients (Group A) and the alternative technique in 19 patients (Group B). In both groups, 700 to 1,000 ml of a crystalloid cardioplegic solution was infused into the aortic root after application of the aortic cross-clamp. In Group A (traditional technique), 500 ml was infused into the aortic root after each distal anastomosis. In Group B (alternative technique), cardioplegic solution was administered through the vein graft after each distal anastomosis, and a proximal anastomosis was constructed after distal anastomoses to the most ischemic regions to permit continued cardioplegic delivery to these regions. The cross-clamp period was shorter in Group A than in Group B (44 +/- 15 versus 60 +/- 18 minutes, p less than 0.01), but the mean temperature in the most ischemic region was warmer (Group A, 19 degrees +/- 3 degrees C; Group B, 15 degrees +/- 3 degrees C, p less than 0.05). The postoperative CK-MB was higher in Group A (Group A, 47 +/- 36; Group B, 21 +/- 9 IU/L, p less than 0.01). Cardiac lactate production persisted longer in Group A (Group A, 4 +/- 1; Group B, 1 +/- 1 hours postoperatively, p less than 0.05). Volume loading 4 hours postoperatively produced a similar increase in left atrial pressure and cardiac index in both groups. In response to volume loading, Group A patients produced lactate, but Group B patients extracted lactate (change in cardiac lactate extraction: Group A, -1.7 +/- 2.3; Group B, +2.5 +/- 5.1 mg/dl, p less than 0.05). The construction of proximal as well as distal anastomoses during a prolonged cross-clamp period permits more uniform cooling and immediate reperfusion. This alternative technique resulted in less injury (CK-MB release) and more rapid recovery of myocardial metabolism.

Aged↗

PubMed1982

Left ventricular function in trained and untrained healthy subjects.

Left ventricular function was compared in 18 normal sedentary controls (mean age 28 years, range 22 - 34 years) and nine endurance-trained athletes (mean age 19 years, range 15 - 25 years) at rest and during supine bicycle exercise. Gated radionuclide angiocardiograms were performed at rest and at each level of graded maximal supine bicycle exercise. Heart rate, blood pressure, left ventricular ejection fraction and the relative changes in left ventricular end-diastolic and end-systolic volumes were assessed. Athletes attained a much greater work load than controls (mean 22.1 kpm/kg body weight vs 13 kpm/Kg body weight). Both groups achieved similar increased in heart rate, blood pressure and ejection fractions. In the controls, the mean end-diastolic volume increased to 124% of that at rest (p less than 0.02) during exercise and the mean end-systolic volume decreased to 81% of the rest level (p less than 0.02). In contrast, the mean end-diastolic volume did not significantly change during exercise in the athletes, and the mean end-systolic volume decreased to 64% of rest (p less than 0.05). Thus, although trained and untrained healthy subjects had similar increases in the left ventricular ejection fraction during exercise, different mechanisms were used to achieve these increases. Untrained subjects increased end-diastolic volumes, whereas trained subjects decreased the end-systolic volumes. The ability of athletes to exercise without increasing preload may be an effect of training amd might have important implications in reducing myocardial oxygen demand during exercise.

Adult↗

PubMed1981

The hemodynamic and metabolic response to pacing after aortocoronary bypass.

Long-term follow-up of aortocoronary bypass has shown good preservation of ventricular function. However, myocardial reserve in the immediate postoperative period may not be optimal. Nineteen patients who underwent elective aortocoronary bypass protected with cold potassium cardioplegia were studied in the early postoperative period at rest and during the stress of atrial and ventricular pacing. Performance was assessed by hemodynamic, metabolic and nuclear angiographic measurements. In the first 2--6 hours after aortic cross clamping, myocardial performance was preserved at rest and there was no evidence of ischemic metabolism. Atrial pacing at a rate of 119 beats/min caused a significant increase in cardiac index (p less than 0.01) without deterioration in hemodynamics, ejection fraction or metabolic status. At the same rate, ventricular pacing did not change the cardiac index and there was a decrease in hemodynamic function. Ejection fraction decreased from 56% to 44% (p less than 0.05) without a change in end-diastolic volume. Lactate, pyruvate and beta hydroxybutyrate extractions were changed to net production. Ventricular performance was preserved at rest immediately after aortocoronary bypass done with multidose cold potassium cardioplegia, with adequate reserve to meet the stress of atrial but not ventricular pacing. We conclude that the therapeutic implications of the type of pacing selected in the immediate postoperative period may be important.

Atrial Function↗