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Biomedical subjects

L W Klein

Publications and source records attributed to L W Klein.

At least 55 records · Page 3Linked to original sources
PubMed1993

Characterization of a saphenous vein graft aneurysm by intravascular ultrasound and computerized three-dimensional reconstruction.

Aneurysmal dilatations in saphenous vein grafts are rare complications of coronary artery bypass surgery that mostly represent thin-wall pseudoaneurysms at anastomotic sites. We describe a case of an enlarging distal saphenous vein graft aneurysm in which intravascular ultrasound (IVUS) and computerized three-dimensional reconstruction (3DR) of the IVUS images was performed to conclusively demonstrate true aneurysm morphology. Although both atherosclerotic and nonatherosclerotic mechanisms for vein graft aneurysm formation have been previously suggested, IVUS images and 3DR of the aneurysm in this case did not reveal any of the features typical for atherosclerotic lesions. Further, the IVUS images and 3DR suggest that progressive atherosclerosis is not the likely cause of aneurysm formation in this case. This application of IVUS and 3DR provides detailed information about saphenous vein graft aneurysm structure, clues to aneurysm formation, and suggests a natural history that may differ from that of pseudoaneurysms.

Aged↗
PubMed1992

Does the AHA/ACC task force grading system predict outcome in multivessel coronary angioplasty?

To assess the ACC/AHA task force grading system as a predictor of outcome in patients undergoing multivessel percutaneous transluminal coronary angioplasty we analyzed all failures (residual stenosis > 50%, Q-wave myocardial infarction, coronary artery bypass grafting during hospitalization, or death) in 97 patients with 328 stenoses. There were 70 males and 27 females; 60 patients had stable angina, and 37 had unstable angina. The mean number of lesions dilated per patient was 3.4 (range 2-8). The mean preangioplasty percent luminal diameter narrowing was 80 +/- 14%. Thirty-eight stenoses were AHA/ACC classification type A, 192 type B, and 98 type C. One hundred twenty-eight lesions were located in the left anterior descending artery or its distribution, 89 in the left circumflex, 96 in the right coronary artery, and 15 in other vessels. Procedural success (< 50% residual diameter narrowing and no major ischemic complications) was achieved in 266 lesions (81.1%). Major ischemic complications (death, myocardial infarction, or emergency bypass surgery) occurred in 8 patients (8.2%) and in-hospital mortality was 2%. Analysis on a per stenosis basis demonstrated 84% success in type A, 89% in type B, and 64% in type C (p < 0.0001). When type B was divided into type B1 (1 type B characteristic) and type B2 (two or more type B characteristics) the success rate was 90% vs. 88% and the complication rate was 1% vs. 2%, respectively (p = n.s.). Logistic regression analysis showed that the best single predictor of failed angioplasty was total occlusion > 3 months, followed by total occlusion < 3 months and severely angulated (> 90 degrees) segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Excimer laser ablation before autoperfusion balloon inflation: a novel therapeutic approach to high grade stenoses in vessels supplying substantial myocardium at risk.

The utility of a novel approach employing excimer laser ablation to form a channel for subsequent autoperfusion balloon angioplasty is presented. Two important advantages of this strategy are highlighted: (1) applicability to severe stenoses in vessels supplying substantial myocardium at risk and (2) ability to allow prolonged inflation time to minimize procedure related ischemia and optimize revascularization of the heart. We prospectively selected and studied five patients and performed excimer laser coronary angioplasty using either a 1.3 mm or 1.6 mm laser catheter followed by autoperfusion balloon dilatation. Procedural success was documented by a significant reduction in mean percent diameter stenosis from 89 +/- 4% (S.D.) to 53 +/- 4% after laser angioplasty (p < 0.0001) and subsequently to 20 +/- 4% after autoperfusion balloon angioplasty (p < 0.0001). Clinical success was attained and characterized by resolution of anginal symptoms for at least 4 weeks after hospital discharge. There were no major acute complications encountered; however, restenosis has occurred in 2 out of 5 patients. We therefore recommend this novel pre-dilation strategy with excimer laser followed by autoperfusion balloon angioplasty in selected patients with an extensive amount of myocardium at risk.

Adult↗
PubMed1992

Intravascular ultrasound in coronary atherosclerosis: a new approach to clinical assessment.

Intravascular ultrasound evaluation of the coronary arteries by means of a selective coronary catheter attached to an ultrasound unit has afforded precise depiction of coronary lumen diameter and area at the level of the catheter tip. The arterial wall at this level can be evaluated for lipid, fibrous tissue, calcification, wall dissections, and intraluminal thrombi. The technique has the advantage over coronary angioscopy and angiography in that it does not require infusions or injections to allow visualization, and it has the ability to depict the inside of the arterial wall. The current disadvantages include the inability to visualize the vessel segments distal to the catheter tip. Three-dimensional reconstruction techniques allow depiction of the segment of the artery traversed by the catheter tip. The use of Doppler ultrasound imaging provides information on coronary flow velocities through coronary obstructions. Intravascular ultrasound images may provide information that complements the coronary arteriogram and may have an impact on patient care and clinical investigation strategies.

Animals↗
PubMed1992

Validation of computerized three-dimensional reconstruction of intravascular ultrasound: measurements of absolute luminal diameter and cross-sectional area in ex vivo human coronary arteries.

UNLABELLED: Computer based 3-dimensional reconstruction transforms 2-dimensional intravascular ultrasound images into a longitudinal format facilitating analysis of luminal narrowing. To validate the accuracy of current software in measuring coronary artery diameter and cross-sectional area, in arteries with atherosclerosis, we performed 3-dimensional reconstruction in 10 human pathologic coronary arterial segments of 10-25mm length. Images were obtained using a 4.8 French catheter with pullback speed of 1mm/sec acquired at 3 frames/sec onto VHS tape. The data were digitized and intraluminal 3-dimensional reconstruction performed using a voxel-based program. Pathologic sections were obtained every 3mm, and dimensions were measured with a resolution of 0.01 mm. Maximum, minimum, and 3 other representative diameters were recorded by an observer blinded to the ultrasound diameters. Average histo-pathologic diameters were reported, and specimen cross-sectional area was then calculated. RESULTS: In 53 sections, pathological diameters ranged from 1.4-4.5mm (mean 2.7 +/- 0.68mm) while 3-dimensional reconstructed diameters were 1.9 to 3.8mm (mean 2.6 +/- 0.54mm). Pathologic and ultrasound derived 3-dimensional reconstruction diameters had an excellent correlation (r=0.86, SEE=+/-0.36). Pathology and 3-dimensional reconstruction cross-sectional area also correlated closely (r=0.88, SEE=+/-1.50). Diameters less than 2.0mm were systematically overestimated and diameters greater than 3.5mm underestimated by 3-dimensional reconstruction. Most 3 dimensional reconstruction values were within +/- 10% of pathology, but diverged at each diameter extreme, approaching +/- 20%. Thus, computerized 3-dimensional reconstruction of ultrasound images shows excellent quantification of luminal size in the 2.0-3.5mm range, suggesting important investigative and clinical applications.

Arteries↗
PubMed1991

Incidence and clinical significance of transient creatine kinase elevations and the diagnosis of non-Q wave myocardial infarction associated with coronary angioplasty.

To assess the incidence and clinical significance of elevated total plasma creatine kinase (CK) and MB isoenzyme fraction after apparently successful coronary angioplasty, a prospective study of 272 consecutive elective procedures was undertaken. Total CK (normal less than 100 IU/liter) and CK MB isoenzyme (normal less than 4%) were measured immediately after successful completion of the procedure and every 6 h for 24 h. All nonelective procedures and results not fulfilling all American Heart Association/American College of Cardiology Task Force guideline criteria for a successful result were excluded from analysis. Of the 272 elective procedures, 249 (92%) were successfully; abnormally elevated CK or CK MB serum levels, or both, were found in 38 (15%) of the successful outcomes. Three patterns of abnormal enzymes were identified: 15 patients with CK greater than or equal to 200 IU/liter and CK MB greater than or equal to 5% (group 1), 4 patients with CK greater than or equal to 200 IU/litter and CK MB less than or equal to 4% (group 2) and 19 patients with CK less than 200 IU/liter and CK MB greater than or equal to 5% (group 3). The three groups were distinguishable by the nature of the complications causing the enzyme release (in particular, the etiology and clinical manifestations). There were significantly more clinically apparent events in group 1 than in the other groups (13 of 15 versus 11 of 23, p less than 0.01) and more events associated with persistent electrocardiographic changes (p = 0.05) and chest pain (p less than 0.05). However, no clinically important sequelae were recognizable in any group at hospital discharge. Thus, abnormal cardiac serum enzyme release after apparently successful coronary angioplasty is 1) relatively common; 2) has many possible causes, including both minor complications and early reversibility of impending major complications; and 3) results in no permanent clinical sequelae.

Adult↗
PubMed1990

Comparative analysis of coronary angiographic morphology following restenosis.

The site and angiographic morphology of restenotic lesions following initially successful coronary angioplasty (PTCA) were compared to the original pre-PTCA stenosis and the immediate post-PTCA result. Forty-seven patients with 55 restenoses were analyzed. All patients with repeat angiography for recurrent ischemia 1 to 12 months post-PTCA documenting restenosis were included. Two orthogonal angiographic views best showing the initial lesion, immediate post-PTCA result, and the restenosis lesion, were selected and matched for angulation and cardiac cycle phase. Individual frames were traced and magnified. Restenosis lesions were similar in morphology to the pre-PTCA lesions in 29 of 55 (53%) and to the post-PTCA lesions in only 25 of 55 (46%) (p = NS). However, when the lesions with residual post-PTCA stenosis of greater than 25% luminal diameter narrowing were excluded from the analysis, the post-PTCA lesion morphology was similar to restenosis morphology in 25 of 30 (83%), whereas pre-PTCA and restenosis morphology was similar in only 15 of 30 (50%) lesions (p less than 0.01). Subgroup analysis revealed that when the restenosis occurred at the same site as the original lesion (group 1), post-PTCA morphology was significantly better (p = 0.01) in predicting restenosis morphology, 15 of 17 (88%), than was pre-PTCA morphology, 8 of 17 (47%). When the restenosis occurred greater than 5 mm distant from the original site (group 2), there was no significant difference in the association between pre-PTCA versus post-PTCA morphology and restenosis morphology. Thus restenosis morphology is usually dissimilar to the pre-PTCA stenosis morphology.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Balloon dilatation of symptomatic subacute intimal dissection presenting as restenosis.

Repeat percutaneous transluminal coronary angioplasty (PTCA) for subacute intimal dissections that produce symptoms after a period of 1 month or more is reluctantly performed for fear of extension and abrupt closure. Patients were identified with demonstrated intimal dissections (intimal contrast staining or frank intimal flap) at the time of initial PTCA who returned a mean of 17.5 weeks (range 9 to 50) later with recurrent chest pain. Repeat angiography revealed luminal compromise due to dissection rather than restenosis in 22 patients. Of these, 17 underwent repeat PTCA. Elective bypass surgery without attempted PTCA was chosen in the other 5 patients because of extensive intimal dissections (greater than 2 balloon lengths) or involvement of critical branches. In the group of 17 patients who had repeat PTCA, 10 (group 1) had a frank intimal flap without persistent contrast staining after the initial PTCA, while 7 (group 2) had both persistent staining and a flap. Successful PTCA was performed in 13 of these 17 patients (76%). There were 2 abrupt closures and 2 unsatisfactory luminal openings. One of these patients required urgent coronary bypass surgery. All 10 group 1 patients had successful repeat procedures versus only 3 of 7 group 2 patients (p = 0.01). The 3 patients with the greatest degree of luminal compromise immediately after the initial PTCA had failed repeat PTCA attempts. These results suggest that repeat PTCA for subacute intimal dissections presenting as restenosis can be successfully performed in selected patients, and that the presence of contrast staining and the degree of luminal compromise by the dissection may be predictive of outcome.

Aged↗
PubMed1989

Adequate heparinization during PTCA: assessment using activated clotting times.

Heparinization during PTCA is often done empirically with an initial 10,000 unit bolus of heparin and subsequent additional boluses as deemed necessary to prevent thrombus formation and fibrin deposition. However, the initial 10,000 unit bolus may not result in adequate systemic anticoagulation in every patient, exposing some patients to risk of thrombus at the angioplasty site and subsequent reocclusion. In this non-randomized study, we assessed systemic coagulation during PTCA by retrospectively analyzing activated clotting times obtained in 108 consecutive patients. All patients had normal baseline prothrombin times and activated partial thromboplastin times. Patients who were on heparin prior to PTCA were excluded. Based on data from studies on heparinization during extracorporeal bypass an activated clotting time (ACT) of greater than 300 seconds was required. Twelve patients (11%) were observed to have activated clotting times of below 300 seconds after an initial 10,000 unit bolus of heparin. These patients required an additional 3,000-10,000 units of heparin to have systemic anticoagulation during PTCA. Symptoms of stable or unstable angina had no significant effect on heparin requirement, although there was a trend toward greater heparin resistance in unstable angina. We conclude that it is important to monitor the status of anticoagulation during PTCA, for 11% of patients undergoing PTCA require additional initial heparin bolus to achieve an ACT greater than 300 seconds and to be effectively anticoagulated. Careful monitoring of heparinization during PTCA may reduce the incidence of thrombosis.

Angina Pectoris↗
PubMed1988

Surgical revascularization of left main coronary artery stenosis: determinants of perioperative and long-term outcome in the 1980s.

The postoperative courses of 176 patients who underwent coronary artery bypass surgery for significant left main coronary artery stenosis were analyzed to determine which preoperative clinical and angiographic factors correlated best with outcome. Clinical variables included age, sex, New York Heart Association (NYHA) anginal class, presence of unstable angina, and surgical class. The angiographic variables included percentage of left main stenosis, presence of right coronary artery stenosis, coronary dominance, number of vessels diseased, myocardial jeopardy score, and ejection fraction. The overall perioperative mortality rate was 9.1%. There was a significant increase in perioperative mortality among female patients (p less than 0.05) and patients undergoing emergency surgery (p less than 0.05). Patients with left main stenosis of 80% or more or with balanced or left dominant circulation showed trends toward increased perioperative mortality. Life-table analysis showed that emergency surgery and left main stenosis of 80% or more correlated with increased long-term mortality (p less than 0.05). No other variable tested showed a significant correlation with either perioperative or long-term mortality. A comparison of these results with studies performed in the 1970s shows that there has been considerable change in those factors which place a patient at increased risk for mortality during surgical treatment of left main coronary artery stenosis.

Aged↗
PubMed1988

The resolution of coronary collaterals after successful percutaneous transluminal coronary angioplasty.

It has been shown that collaterals can develop rapidly during acute coronary occlusion, either due to thrombosis or during angioplasty (PTCA). However, the fate of well-developed collaterals immediately after a successful PTCA is unknown. Accordingly, 15 patients with Rentrop class 2 or 3 collaterals as visualized angiographically were studied immediately after successful single-vessel PTCA. The left anterior descending artery contained the stenosis in nine patients and the right coronary contained the stenosis in six patients. There was total occlusion of six vessels and subtotal occlusions of nine vessels pre PTCA. Immediately after PTCA, flow through the collaterals to the stenosed artery could no longer be visualized angiographically in eight patients (group 1), but remained faintly visible in seven patients (group 2). There was no difference between these two groups with regard to pre PTCA transstenotic pressure gradient (46 +/- 12 vs 42 +/- 14 mm Hg), post PTCA pressure gradient (13 +/- 7 vs 11 +/- 10 mm Hg), or post PTCA percent luminal diameter narrowing (26 +/- 18% vs 24 +/- 13%). These findings suggest that despite similar hemodynamic and angiographic improvement, the resolution of collaterals immediately after PTCA is variable.

Angioplasty, Balloon↗
PubMed1988

A non-linear elastic model of contraction of ischaemic segments.

Previous studies have characterised the motion of the myocardium using a linear time varying elastance model, ie, they have sought to characterise the relationship between left ventricular volume and internal pressure as linear, but with time varying slopes over the cardiac cycle. However, the motion of myocardium during regional ischaemia has not been characterized by such models. Studies of totally ischaemic tissue and of myocardium in diastole have characterised the relationship between tension or stress and segment length as exponential. It is the purpose of this study to present a new model in which myocardial contraction is expressed as an exponential, but time varying elastic relationship. In this model tension, T, is related to segment length according to the formula T = e alpha(t)L + beta, where alpha(t) rises with systole and falls in diastole. This model was applied to the motion of hypokinetic segments noted in a series of conscious dogs studied for other purposes. Hypokinetic segments display early systolic bulging, decreased systolic shortening, and early diastolic recoil. These particular types of segment motion are naturally predicted by this model. Furthermore, the motion of myocardial segments as they become increasingly ischaemic may be predicted, including a gradual shift to the right and narrowing of the tension-length loop. alpha was noted to be independent of loading change, and thus may be viewed as an index of contractility. This model thus predicts the pattern of motion of hypokinetic segments and provides new insight into myocardial contractility.

Animals↗
PubMed1988

Contractile function and reserve during acute ischaemia in the canine lateral border zone.

The hypothesis that there is a lateral border zone with function intermediate to adjacent ischaemic and non-ischaemic tissue was tested in 10 open chest anaesthetised dogs. Four pairs of segment length crystals were placed in parallel so as to span the ischaemic and non-ischaemic zones. Graded occlusion was produced with a screw clamp applied to a carotid to left anterior descending artery cannulation system. Contractile reserve was assessed using postextrasystolic potentiation. A balloon perfusion labelling system was used to label negatively the potentially ischaemic zone and quantify the admixture of ischaemic and non-ischaemic tissue in the lateral border zone, defined by the fraction of normal zone tissue. When the 40 crystal pairs from the 10 dogs were grouped according to fraction of normal zone tissue (FNZT), 13 were in the central ischaemic zone (FNZT less than 0.1), seven were in the border ischaemic zone (FNZT 0.1-0.5), five were in the border non-ischaemic zone (FNZT 0.5-1.0), and 15 were in the non-ischaemic zone (FNZT 1.0). When the lateral border zone is predominantly non-ischaemic tissue, the tissue behaves as though it is non-ischaemic. Segmental shortening before and after postextrasystolic potentiation in the border non-ischaemic zone and non-ischaemic zone did not change with ischaemia. When tissue in the lateral border zone is predominantly ischaemic, it behaves as though it is ischaemic. Segmental shortening decreased in parallel with progressive ischaemia in the border ischaemic zone and ischaemic zone. At total occlusion, segmental shortening in the border ischaemic zone was -2.3(5.9%) and in the ischaemic zone -3.5(3.6)% (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Augmentation of contraction in remote nonischemic zone during acute ischemia.

We studied how left ventricular loading conditions and the size of the ischemic zone affect regional segmental shortening (% delta L) in ischemic (IZ) and remote nonischemic zones (NZ) after acute coronary occlusion. Distal and proximal portions of the left anterior descending artery (group I, 10 dogs) or the left circumflex artery (group II, 10 dogs) were occluded in two stages. Segment length sonomicrometers were placed in the distal and proximal IZ and in the distal and proximal NZ. % delta L was divided into isovolumic and ejection phases. Left ventricular end-diastolic pressure (LVEDP) was decreased 3 +/- 1 mmHg by blood withdrawal and then increased 6 +/- 2 mmHg by blood transfusion before and after distal and proximal coronary occlusions. LVEDP was brought back to its initial value before distal and proximal coronary occlusions. Regional blood flow and total blood flow deficit were measured with microspheres. Similar results were obtained in group I and II experiments. After coronary occlusion, the IZ showed systolic bulging occurring primarily in isovolumic systole. In the NZ, total and isovolumic % delta L increased from control, whereas ejection % delta L did not change. As LVEDP was raised, IZ isovolumic bulging decreased and ejection % delta L was unchanged, whereas NZ isovolumic % delta L decreased and ejection % delta L increased. Thus IZ bulging and NZ isovolumic % delta L changed in opposite directions when load was varied. The larger IZ after proximal coronary occlusion tended to increase the amount of NZ isovolumic % delta L. In conclusion, at low LVEDP NZ augmentation is predominantly caused by an increase in isovolumic % delta L, whereas if LVEDP is increased it is because of an increase in ejection % delta L. In addition, in open-chest animals augmented contraction in the NZ may be related to the size of the IZ.

Acute Disease↗
PubMed1988

Quantification of absolute luminal diameter by computer-analyzed digital subtraction angiography: an assessment in human coronary arteries.

Determination of absolute lumen diameters has been shown to be useful in predicting the functional importance of a coronary stenosis. In this study, both single-plane and orthogonal biplane digital subtraction angiograms were obtained in human cadaver coronary arteries. A single absolute diameter was calculated at the site of greatest narrowing in 20 segments by two automated computerized algorithms. Minimum and maximum diameters at the site of the stenosis were measured from pathologic sections prepared after pressure fixation. Method 1, which determines the edges by means of the first derivative of the videodensity curve, derived absolute diameters that fell between the pathologic minimum and maximum in 10 of 20 segments. Method 2, which determines the edges by an average of the first and second derivatives of the videodensity change, derived absolute diameters that fell between the pathologic minimum and maximum diameters in 15 of 20 segments. Method 1 correlated well with the maximum pathologic diameter (r = .76) and less well with the minrmum pathologic diameter (r = .67). Method 2 correlated very well with the maximum pathologic diameter (r = .79) and also correlated well with the minimum pathologic diameter (r = .74). As would be expected, the computerized algorithms tended to overestimate the minimum pathologic diameter and to underestimate the maximum pathologic diameter. In six segments, two orthogonal views were analyzed; no further accuracy was discernible over single-plane determinations. Thus quantitative coronary angiography by digital subtraction angiography is sufficiently accurate to be of use in the measurement of the severity of a coronary stenosis.

Coronary Angiography↗