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Biomedical subjects

R W Smalling

Publications and source records attributed to R W Smalling.

At least 73 records · Page 4Linked to original sources
PubMed1993

Percutaneous transluminal balloon aortic and mitral valvuloplasty in 27 patients treated at Hermann Hospital.

Percutaneous aortic and mitral valvuloplasty are recognized as alternative interventions in cases of severe symptomatic aortic and mitral stenosis. We described the acute hemodynamic results, immediate clinical outcomes, and complications in 27 patients treated consecutively at Hermann Hospital with either percutaneous balloon aortic or mitral valvuloplasty. We review the possible mechanisms of action of balloon valvulotomy and the current indications for either procedure. Balloon aortic valvuloplasty is indicated in elderly patients with severe aortic stenosis in whom open-heart surgery is contraindicated or carries excessive mortality. All patients with symptomatic mitral stenosis are potential candidates for balloon mitral valvulotomy. In centers with an experienced interventional team in transseptal catheterization and an active surgical program, balloon valvulotomy is the initial procedure of choice for significant mitral stenosis with mobile leaflets and minimal chordal thickening.

Adolescent↗
PubMed1992

Improved regional myocardial blood flow, left ventricular unloading, and infarct salvage using an axial-flow, transvalvular left ventricular assist device. A comparison with intra-aortic balloon counterpulsation and reperfusion alone in a canine infarction model.

BACKGROUND: It has been suggested that left ventricular unloading at the time of reperfusion provides superior infarct salvage over reperfusion alone. The purpose of this study was to show that the Hemopump transvalvular axial-flow left ventricular assist device provides superior left ventricular unloading, ischemic zone collateral blood flow, and infarct size reduction compared with intra-aortic balloon counterpulsation and reperfusion alone. METHODS AND RESULTS: Eighteen dogs were instrumented with regional myocardial function sonomicrometers in the ischemic and control zones. The left anterior descending coronary artery just distal to the first diagonal branch was instrumented with a silk snare and Doppler flow probe. Additionally, pressure catheters were placed in the left atrial appendage, left ventricular apex, and ascending aorta for hemodynamic measurements. Regional myocardial blood flow was determined by using 15-microns radioactive microspheres. Measurements were made in the control state, immediately after coronary occlusion, at 1 and 2 hours after coronary occlusion, with reperfusion, and 1 hour after reperfusion. In treated animals, left ventricular assistance was maintained during the entire period of occlusion and reperfusion. The Hemopump was associated with a significant decrease in left ventricular systolic and diastolic pressure, whereas mean arterial pressure was maintained. Intra-aortic balloon counterpulsation resulted in no significant changes in left ventricular systolic pressure and a modest decrease in left ventricular diastolic pressure. Regional unloading as assessed by sonomicrometers was significant in the Hemopump animals and absent in the balloon pump animals. Absolute regional myocardial blood flow in the ischemic zone increased slightly (p = 0.002) in the Hemopump animals and did not change in the balloon pump animals. Infarct size expressed as percentage of the zone at risk was 62.6% in the control animals, 27.22% in the balloon pump animals, and 21.7% in the Hemopump animals. CONCLUSIONS: Mechanical unloading of the ventricle during ischemia and reperfusion appears to result in significant infarct salvage compared with reperfusion alone. The Hemopump appears to provide superior left ventricular systolic and diastolic unloading compared with intra-aortic counterpulsation in a canine model.

Animals↗
PubMed1991

Effects of rotational atherectomy in normal canine coronary and diseased human cadaveric arteries: potential for plaque removal from distal, tortuous, and diffusely diseased vessels.

To test the hypothesis that tortuous, diseased vessels could be successfully treated with a flexible rotational atherectomy device we evaluated the BARD atherectomy device with quantitative angiography and histology in normal canine coronary arteries and diseased human below-knee amputation specimens. The mid left anterior descending and the circumflex vessels were treated in 4 dogs serially with 1 wk separating treatments. The acute and follow-up anterior descending artery size was unchanged (1.41 mm before, 1.39 mm after, and 1.59 mm at 1 week). Similar findings were obtained in the circumflex vessels. In 4 adult human amputated legs, diseased peroneal or tibial arteries were treated with a significant reduction in the percent luminal diameter stenosis from 62.75 prior to intervention to 36.5 following intervention (p = 0.021). The luminal diameter increased from 0.81 to 1.54 mm (p = 0.06). In 2 canine arteries there was histologic evidence of localized perforation of the arterial wall, but there was no angiographic evidence of perforation or dissection and no significant myocardial necrosis in the distribution of the treated vessels at 1 wk. The majority of the diseased human vessels demonstrated smoothly cut atheromas with sparing of the media. The rotational atherectomy catheter system holds promise for removal of plaque in relatively small, diffusely diseased, tortuous vessels.

Animals↗
PubMed1991

Treatment of cardiogenic shock with the Hemopump left ventricular assist device.

A multiinstitutional study is in progress to evaluate the Hemopump in the treatment of cardiogenic shock. Fifty-three patients with refractory cardiogenic shock were selected for Hemopump assistance. The hemodynamic definition of cardiogenic shock included (1) a cardiac index of less than 2.0 L.min-1.m-2, (2) pulmonary capillary wedge pressure of greater than 18 mm Hg, and (3) a systolic blood pressure of less than 90 mm Hg or a left ventricular work index of less than 1,500 g-m.m-2.min-1. The Hemopump was successfully inserted in 41 of 53 patients (77.3%). A significant improvement in the hemodynamic status was seen during Hemopump assistance. A minimal level of hemolysis was observed. No leg ischemia was observed. The 30-day overall survival of the Hemopump group was 31.7%. Criteria establishing indications for use and clinical utility are proposed. We conclude that the Hemopump provides significant hemodynamic support of the patient in cardiogenic shock allowing for recovery from ventricular stunning in marginal ventricles, and that in select patients the Hemopump may offer a major improvement in survival over conventional therapy.

Cardiac Output↗
PubMed1991

Patterns in visual interpretation of coronary arteriograms as detected by quantitative coronary arteriography.

In part 1 of a three-part study, 14 novice readers and 6 experienced cardiologists interpreted phantom images of known stenosis severity. No difference between the interpretations of experienced and novice readers was detectable. Visual estimates of "moderately" severe stenosis were 30% higher than actual percent diameter stenosis. In part 2 of the study, visual interpretation of percent diameter stenosis from 212 stenoses on 241 arteriograms was compared with quantitative coronary arteriographic assessment. The visual analysis overestimated disease severity in arteries with greater than or equal to 50% diameter stenosis (except for right coronary lesions) and underestimated severity in all arteries with less than 50% diameter stenosis. Of the 241 arteriograms, 40 had quantitative and visual analysis of all three coronary arteries for assessment of significant disease. In only 62% of the cases did visual and quantitative methods agree on the presence of severe disease; visual estimates diagnosed significantly (p less than 0.05) more three-vessel disease. In part 3 of the study, comparison of percent diameter stenosis by visual estimate with quantitative coronary arteriographic assessment before and after balloon angioplasty of 38 stenoses showed that visual interpretation significantly (p less than 0.001) overestimated initial lesion severity and underestimated stenosis severity after angioplasty.

Angiography↗
PubMed1991

Myocardial metabolism of fluorodeoxyglucose compared to cell membrane integrity for the potassium analogue rubidium-82 for assessing infarct size in man by PET.

Potassium loss from damaged myocardial cells is linearly related to CPK enzyme loss reflecting extent of necrosis. The potassium analog, rubidium-82 (82Rb), is extracted after i.v. injection and retained in viable myocardium but is not trapped or washed out of necrotic regions. To compare myocardial cell metabolism with membrane dysfunction as indicators of necrosis/viability, 43 patients with evolving myocardial infarction and coronary arteriography had positron emission tomography using fluorodeoxyglucose (FDG) and the potassium analog 82Rb. Percent of heart showing FDG defects and 82Rb washout on sequential images indicating failure to retain the potassium analogue were visually assessed and quantified by automated software. Infarct size based on rubidium kinetics correlated closely with size and location on FDG images (visual r = 0.93, automated r = 0.82), suggesting that loss of cell membrane integrity for trapping the potassium analog 82Rb parallels loss of intracellular glucose metabolism, both comparable quantitative markers of myocardial necrosis/viability.

Carbohydrates↗
PubMed1990

Improved infarct-related arterial patency after high dose, weight-adjusted, rapid infusion of tissue-type plasminogen activator in myocardial infarction: results of a multicenter randomized trial of two dosage regimens.

To determine whether a weight-adjusted high dose (2 mg/kg body weight over 3 h) rapid infusion of recombinant tissue-type plasminogen activator (rt-PA) was more efficacious than a weight-adjusted standard dose (1.25 mg/kg over 3 h) in achieving reperfusion in the setting of acute myocardial infarction, 175 patients were entered into a randomized multicenter trial. Eighty-four patients were entered into the high dose group, receiving 1.2 mg/kg (10% given as a bolus injection) over 1 h, followed by 0.8 mg/kg over the next 2 h. Ninety-one patients were given 0.75 mg/kg (10% given as a bolus injection) in 1 h, followed by 0.5 mg/kg administered over the next 2 h. The median dose in the group that received 2 mg/kg dose was 145 mg, compared with 100 mg in the group that received 1.25 mg/kg. The 90 min patency rate in the group that received 2 mg/kg was 84% compared with 70% in the group that received 1.25 mg/kg (p = 0.003). Sixty-four percent of the patients in each group underwent coronary angioplasty at the time of cardiac catheterization. The infarct-related artery patency rate at the end of catheterization was 91% in the group that received 2 mg/kg compared with 83% in the group that received 1.25 mg/kg (p = 0.08). Among patients with a patent infarct-related coronary artery after catheterization, the 6 month mortality rate in the group that received 2 mg/kg was 2.9% compared with 9.8% in the group that received 1.25 mg/kg (p = 0.15). The bleeding complication rate in the two groups was similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Assessment of coronary artery disease severity by positron emission tomography. Comparison with quantitative arteriography in 193 patients.

To assess the accuracy of positron emission tomography (PET) for evaluation of coronary artery disease (CAD), cardiac PET perfusion images were obtained at rest and with dipyridamole-handgrip stress in 193 patients undergoing coronary arteriography. PET images were reviewed by two independent readers blinded to clinical data. Subjective defect severity scores were assigned to each myocardial region on a 0 (normal) to 5 (severe) scale. Results were compared with arteriographic stenosis severity expressed as stenosis flow reserve (SFR), with continuous values ranging from 0 (total occlusion) to 5 (normal), calculated from quantitative arteriographic dimensions using automated detection of the vessel borders. There were 115 patients with significant CAD (SFR less than 3), 37 patients with mild CAD (3 less than or equal to SFR less than 4), and 41 patients with essentially normal coronaries (SFR greater than or equal to 4). With increasingly severe impairment of stenosis flow reserve, subjective PET defect severity increased. Despite wide scatter, a PET score of 2 or more was highly predictive of significant flow reserve impairment (SFR less than 3). For each patient, the score of the most severe PET defect correlated with the SFR of that patient's most severe stenosis (rs = 0.77 +/- 0.06). For each of 243 stenoses, PET defect score correlated with the SFR of the corresponding artery (rs = 0.63 +/- 0.08). PET defect location closely matched the region supplied by the diseased artery, and readers agreed whether the most severe PET defect was less than or more than 2 for 89% of patients.

Angiography↗
PubMed1989

Acute MI: role of thrombolysis and intervention.

Several issues confront the physician treating the patient with an acute infarction. If the patient is a thrombolytic candidate, a 20 to 30 per cent failure rate still exists, and it is difficult to predict on clinical grounds who has had a successful trial of thrombolytics or not; therefore, considerable clinical judgment must be applied. If the patient has relief of pain and diminished ST segment elevation, it is likely that thrombolytic therapy has been successful. Limitations concerning the benefits of thrombolytic or angioplasty therapy for the acute infarction also exist with regard to baseline patient characteristics. Older patients, especially women, seem to have more complications and less beneficial results from acute revascularization than do others. Patients with anterior infarctions as compared with posterior or inferior wall infarctions probably have a higher benefit from intracoronary thrombolysis. The acute myocardial infarction patient can be treated in multiple ways. Based on the preceding information and our own clinical experience, some recommendations can be made. Other sources with their own recommendations are available as well. First, because of the uncertainty still present in deciding optimum therapy for any given patient, as many patients as possible should be included in randomized prospective clinical trials that are now ongoing. If the patient or treating physician elects not to take part in such a trial, much of the therapy will be based on available resources. In small hospitals without acute catheterization or angioplasty facilities, intravenous thrombolytic therapy should be instituted as quickly as possible. In patients who are not able to receive thrombolytic therapy, acute catheterization with consideration for either angioplasty or acute bypass surgery should be undertaken if the patients are relatively young and early on in their course. Treatment of older patients, especially women, should be tempered by the knowledge that there are diminishing returns in aggressive approaches to these patients. It would appear that the presence of cardiogenic shock itself, although a predictor of higher cardiac mortality, should not preclude an aggressive approach and indeed this patient may benefit greatly from revascularization as well as pharmacologic and mechanical support of the cardiovascular system. If thrombolytic therapy without catheterization is undertaken, there remains the potential for either nonrevascularization or early closure.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiography↗
PubMed1989

Effect of the hemopump left ventricular assist device on regional myocardial perfusion and function. Reduction of ischemia during coronary occlusion.

The Hemopump is a new 7-mm diameter left ventricular assist device that provides as much as 3.5 l/min of nonpulsatile cardiac output after fluoroscopic placement into the left ventricle through a femoral artery cutdown. The purpose of this study was to measure the effects of Hemopump assist on hemodynamics, left ventricular function, and perfusion in the presence and absence of ischemia. Eight dogs were instrumented under pentobarbital anesthesia with left ventricular, left atrial, and aortic catheters, a loose silk ligature around the midleft anterior descending coronary artery, and sonomicrometer crystals in midwall myocardium within the left anterior descending and circumflex perfusion territories. Hemodynamic variables, regional systolic fractional shortening, and myocardial perfusion after left atrial injection of 15-microns radiolabeled microspheres were measured in the presence and absence of Hemopump assist before and after left anterior descending artery occlusion. In the absence of ischemia, Hemopump left ventricular assist resulted in reduced left ventricular end-diastolic pressure while aortic mean pressure was maintained, and there was significant reduction in regional systolic fractional shortening (reflecting systolic unloading) that correlated with an 18% decline in regional myocardial perfusion. During left anterior descending artery occlusion, left ventricular systolic and diastolic pressures were reduced during Hemopump assist while aortic mean pressure was maintained. Perfusion rose in the ischemic territory (from 13.0 +/- 8.7% to 26.2 +/- 19.8% of nonischemic flow, p = 0.045). Reduced fractional shortening was again seen in nonischemic tissue with Hemopump assist during left anterior descending artery occlusion, and this was often correlated with reduced perfusion (r = 0.67).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Factors affecting outcome of coronary reperfusion with intracoronary streptokinase in acute myocardial infarction.

Aggressive interventional therapy in acute myocardial infarction (AMI) is expensive, time-consuming and not without significant risk. To determine which patients are most likely to benefit from such therapy, the effects of patient age, reperfusion success, admission left ventricular (LV) function, infarct location, admission clinical class, time from onset of pain to reperfusion and admission electrocardiographic findings on the outcome of coronary reperfusion in AMI were assessed in 292 prospectively studied, sequential patients from August 1980 to January 1984. Two hundred ten patients received intracoronary streptokinase (SK) therapy on admission and 82 patients, who either refused the protocol or met exclusion criteria, served as control subjects. Patients older than 65 years showed little improvement in 1-year mortality risk and no significant improvement in LV function during hospitalization after treatment with intracoronary SK. The remaining patients, 178 treated with SK and 48 control, were well matched and served as the basis for further comparisons. In this subgroup of patients, reperfusion success was associated with improved survival and LV function (mortality rate 3%, vs 17% in control subjects; increase in ejection fraction [EF] 18% vs 4%). Patients with an EF of less than 45% on admission showed a 21 +/- 30% increase in EF, compared with an increase in control subjects of 8 +/- 19%, and a lower 1-year mortality rate than controls (6% vs 21%, p = 0.01). Patients with anterior AMI had a significant increase in EF in the SK group (22 +/- 31%) and lower mortality compared with control subjects (5% vs 25%, p = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

A multicenter, randomized, placebo-controlled trial of a new form of intravenous recombinant tissue-type plasminogen activator (activase) in acute myocardial infarction.

A new, predominantly single chain preparation of recombinant tissue-type plasminogen activator was evaluated to determine coronary thrombolytic efficacy in 100 patients with acute myocardial infarction. At 3.6 +/- 1.2 hours (mean +/- SD) from symptom onset, patients received either intravenous tissue plasminogen activator (1.25 mg/kg body weight over 3 hours) or placebo on a 3:1 randomized, double-blind basis. Coronary angiography, performed 68 +/- 13 minutes after initiation of the study drug infusion, demonstrated patency of the infarct-related artery in 40 (57%) of 70 patients in the tissue plasminogen activator group compared with 3 (13%) of 23 patients in the placebo group (p less than 0.001). Patients in the placebo group were then eligible to receive intracoronary streptokinase. At 90 minutes the patency was observed in 49 (69%) of 71 tissue plasminogen activator patients compared with 5 (24%) of 21 placebo patients (p less than 0.001). At 120 minutes patency was observed in 59 (79%) of 75 patients of the tissue plasminogen activator group and in 10 (40%) of 25 in the intracoronary streptokinase/placebo group. A nadir value of less than 100 mg/dl fibrinogen occurred in 8 (11%) of 73 patients receiving tissue plasminogen activator versus 8 (40%) of 20 patients treated with intracoronary streptokinase (p = 0.002). Moderate or severe bleeding episodes occurred in 39% of patients treated with tissue plasminogen activator compared with 32% of patients who received placebo/intracoronary streptokinase (p = NS). Thus, this tissue plasminogen activator preparation achieves a high rate of recanalization and, at the doses employed, exhibits increased fibrinogen sparing compared with intracoronary streptokinase.

Angiography↗
PubMed1987

Relation between geometric dimensions of coronary artery stenoses and myocardial perfusion reserve in man.

To determine the relation between stenosis anatomy and perfusion in man, 31 patients had quantitative coronary arteriography and positron imaging (PET) with Rb-82 or N-13 ammonia at rest and after dipyridamole-handgrip stress. 10 patients were also studied after angioplasty (total stenoses = 41). Percent narrowing and absolute cross-sectional luminal area were related through a quadratic function to myocardial perfusion reserve determined with PET. Arteriographically determined coronary flow reserve was linearly related to relative myocardial perfusion reserve as expected, based on the derivation of equations for stenosis flow reserve. All of the correlations had considerable scatter, indicating that no single measurement derived by coronary arteriography was a good indicator of perfusion reserve by PET in individual patients. This study provides the relation between all anatomic dimensions of coronary artery stenoses and myocardial perfusion reserve in man, and suggests that PET indicates the functional significance of coronary artery stenoses for clinical purposes.

Arterial Occlusive Diseases↗
PubMed1987

Changes in myocardial perfusion reserve after PTCA: noninvasive assessment with positron tomography.

The effect of percutaneous transluminal coronary angioplasty (PTCA) on myocardial perfusion reserve has not been previously determined. Accordingly, 11 patients underwent positron imaging with [13N]ammonia or 82Rb at rest and following dipyridamole + handgrip stress before and after PTCA. The ratio of stress to rest activity (S:R) was determined for each region of interest. Relative myocardial perfusion reserve by positron tomography (RMPR) was calculated by dividing S:R of the stenotic area by a corresponding value from a normal reference area of the same patient. Automated quantitative coronary arteriography was used to objectively measure the percent diameter (%D) and the percent area narrowing (%A) of the stenoses. In nine patients with successful PTCA, %D and %A improved (68 +/- 10 to 49 +/- 15% and 92 +/- 3 to 72 +/- 5%) and RMPR increased from 0.79 +/- 0.07 to 0.96 +/- 0.05. In the two patients in whom PTCA was unsuccessful, RMPR was unchanged. Changes in RMPR correlated inversely with changes in %D (r = -0.68) and %A (r = -0.92) and directly with improved coronary flow reserve derived from all stenosis measurements (r = 0.73, p less than 0.001 for each). This study suggests that dipyridamole + handgrip stress imaging with PET can be used to assess changes in myocardial perfusion reserve before and after PTCA with the potential for determining restenosis noninvasively.

Adult↗
PubMed1987

The use of pressure-volume curves to assess the mechanism and adequacy of stenosis dilatation by balloon angioplasty.

This report introduces a new technique for monitoring and understanding the mechanical events taking place during coronary balloon angioplasty. A standard inflation syringe is instrumented with transducers to record intra-balloon pressure and volume during stenosis dilatation. The theoretical and practical aspects of obtaining and interpreting PTCA "pressure-volume" curves are described. Based on mechanical principles, this method may provide the PTCA operator with information regarding the stiffness and resilience of each stenosis, the mechanism of dilatation, and a measure of adequacy of lumen enlargement even before the balloon is deflated.

Angioplasty, Balloon↗