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Biomedical subjects

K M Kent

Publications and source records attributed to K M Kent.

At least 199 records · Page 11Linked to original sources
PubMed1989

Transient alterations of the QRS complex and ST segment during percutaneous transluminal balloon angioplasty of the right and left circumflex coronary arteries.

The dynamic QRS amplitude changes that appear during 1-vessel percutaneous transluminal coronary angioplasty of the right and left circumflex coronary arteries were studied in 20 patients using continuous 3-lead electrocardiographic recordings representing leads aVF, V2 and V5. The balloon inflations that produced the greatest extent of ST-segment deviation were identified for each lead ("maximally ischemic periods"). QRS amplitude measurements were performed manually at both the PR and shifted J-ST baselines at 10-second intervals during these periods to determine that baseline from which the R and S waves most nearly maintained their control amplitudes. There was no significant baseline relation for either the R or the S waves in leads V2 and V5 during ischemia. However, the R-wave changes in lead aVF were significantly associated with the PR- versus the J-ST-segment baseline (p = 0.007); the S wave, when it occurred, had no tendency for either baseline. The electrocardiographic records were also examined visually for characteristics of left posterior (inferior) "periischemic block" likely to occur uniquely in patients with a dominant right or left circumflex occlusion. There were 2 patients with obstruction of the right circumflex artery who exhibited the characteristics of periischemic block during percutaneous transluminal coronary angioplasty, as evidenced by an increase in R-wave duration, amplitude or both in lead aVF.

Adult↗
PubMed1989

Recurrent ischemia more than 1 year after successful percutaneous transluminal coronary angioplasty. An analysis of the extent and anatomic pattern of coronary disease.

Of 1,181 consecutive patients who underwent successful percutaneous transluminal coronary angioplasty (PTCA) as an initial revascularization procedure and who had at least 1 year of asymptomatic follow-up, 66 (6%) underwent repeat angiography because of recurrent symptoms or evidence of exercise-induced ischemia. Patients who had revascularization procedures within 1 year of PTCA were not included in the analysis. Mean time to recurrent ischemia was 30.8 +/- 17.4 months (range 12-89 months). At follow-up, 47 patients had angina, 13 had atypical chest pain, two had acute myocardial infarction, and four had positive exercise tests without symptoms. No patient showed spontaneous regression in the extent of coronary artery disease (CAD). As compared with the extent of CAD immediately after PTCA, the extent of CAD at follow-up did not change in 26 patients (39%); it increased by one vessel in 30 (45%), by two vessels in seven (11%), and by three vessels in three (5%). The pattern of CAD seen at follow-up compared with that seen after PTCA was as follows: 18 patients (27%), no change; seven (11%), restenosis only; 30 (45%), progression of CAD at other sites only; and 11 (17%), a combination of restenosis and progression of CAD at other sites. The time to recurrence of ischemia was significantly different between those with restenosis only versus those with progression only (20.1 +/- 9.2 vs. 38.3 +/- 18.5 months) (p less than 0.009). Progression of CAD was equally distributed between dilated and nondilated vessels; however, when progression occurred in the PTCA vessel, it was significantly more likely to be distal to the PTCA site (p less than 0.008).

Angioplasty, Balloon, Coronary↗
PubMed1988

Restenosis after percutaneous transluminal coronary angioplasty.

Restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) occurs 4 to 6 months after the procedure in 25 to 30% of the patients. Although PTCA has become far more effective with improved primary angiographic success rates and decreased complication rates, restenosis rates have not changed since the initial experience. Recurrent arterial stenoses appear to be due to fibrocellular proliferation at the site of the initial PTCA. This proliferative response is probably due to platelet adhesion and subsequent activation of the usual tissue injury responses. Fortunately, restenosis seems to be confined to the period soon after the initial PTCA since the long-term, 3- to 8-year studies demonstrate that restenosis occurs infrequently after that. There are certain predisposing characteristics of patients for restenosis: men with a short duration of symptoms with disease of the proximal left anterior descending arteries who are diabetic and continue to smoke cigarettes after PTCA. Inadequate dilatation of the arteries by PTCA and procedures that result in smooth dilatations without any evidence of dissection are associated with increased risk of restenosis. However, most of these patient and procedural characteristics are not controllable. Studies in which procedural and postprocedural variables have been manipulated have been disappointing. Currently, no alterations in techniques or pharmacologic management have proved effective in decreasing the incidence of restenosis.

Angioplasty, Balloon↗
PubMed1988

Coronary dissection: a predictor of restenosis?

To determine if arterial dissection resulting from transluminal coronary angioplasty (TCA) leads to a greater incidence of restenosis, 273 consecutive patients who had undergone TCA with at least 1 year of follow-up were examined. Success was graded as a greater than or equal to 20% increase in intraluminal diameter. Dissection was defined as a prominent intimal defect at the site of angioplasty. Restenosis was defined as a 50% loss of the initial angiographic gain. Of 216 patients in whom TCA was successful, 64 (30%) had dissections at the site of angioplasty and 152 (70%) had no dissection. During follow-up, 135 patients were asymptomatic with normal results of exercise tolerance tests, recurrent symptoms developed in 81 patients, and 64 patients underwent repeat angiography. The overall restenosis rate was 21%. In the dissection group, 11 (18%) had documented restenosis and 49 (82%) did not develop restenosis. In the nondissection group, 35 (24%) had documented restenosis and 113 (76%) did not develop restenosis. These data show that patients who develop dissections at the time of TCA are no more likely to develop restenosis during follow-up.

Aged↗
PubMed1988

Quantitative ST-segment recovery following angiographically successful angioplasty: a useful warning of early complications.

The angiographic/anatomic appearance of the TCA site and transstenotic gradient trending are two available intraprocedural variables that help to identify patients at high risk for early complications after successful angioplasty. We have reported on an additional variable, the rate of ST recovery following the final balloon deflation as a physiologic marker to identify patients at risk for early complications. Slow ST recovery was present in 52% of patients with early complications of myocardial infarction, urgent or emergent coronary bypass surgery, and/or death, whereas normal ST recovery was seen in 97% of patients with uncomplicated courses. ST trending is a non-invasive modality that is available in all patients undergoing TCA and should be a useful adjunct in identifying patients at high and low risk for early major complications following angiographically successful angioplasty. A prospective study of ST recovery during TCA deserves consideration.

Angioplasty, Balloon↗
PubMed1988

Comparison of complications during percutaneous transluminal coronary angioplasty from 1977 to 1981 and from 1985 to 1986: the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry.

Because the effects of changing technology in percutaneous transluminal coronary angioplasty, increased operator experience and use of the procedure in patients with extensive disease are unknown in regard to complication patterns, the initial 1977-1981 cohort and the recent 1985-1986 cohort of the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty Registry were analyzed with respect to complications. Compared with the initial cohort of 1,155 patients, the 1,801 new cohort patients were older and had an increased prevalence of multivessel coronary artery disease, depressed left ventricular function and prior infarction. Overall complication rates in the recent cohort were either unchanged or decreased from the rates in the initial cohort despite a higher risk patient population. The most significant decreases were in the incidence of coronary spasm (p less than 0.001) and the need for emergency coronary bypass surgery (p less than 0.01). Overall in-hospital mortality was low but was dependent on the extent of vessel disease--0.2% for single vessel disease, 0.9% for double vessel disease and 2.2% for triple vessel disease (p less than 0.001 for linear trend). Acute coronary complications of branch occlusion, dissection or abrupt closure were associated with increased rates of death, nonfatal infarction or need for emergency surgery. Factors showing a multivariate association with increased mortality included a history of congestive heart failure (p less than 0.001), age greater than or equal to 65 years (p less than 0.01), triple vessel or left main coronary artery disease (p less than 0.05), female gender (p less than 0.05) and new onset angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1988

Noninvasive assessment of patients following coronary artery angioplasty.

PTCA alters the natural history of coronary artery disease and thus presents a challenge for the cardiologist to detect the variety of changes that may occur. Continuous electrocardiographic monitoring with automatic detection of ST segment changes has proved valuable during the immediate post-PTCA procedure. Radionuclide ventriculography and thallium-201 perfusion scans are most important in providing physiologic evidence of improved functional blood flow, particularly in patients with limited revascularization. Finally, the important unsolved problem with PTCA, that of restenosis, is best detected by repeat noninvasive testing in the first months after successful PTCA.

Angioplasty, Balloon↗
PubMed1987

Late angiographic follow-up after successful coronary arterial thrombolysis and angioplasty during acute myocardial infarction.

Emergency percutaneous transluminal coronary angioplasty (PTCA) is accepted as an important reperfusion intervention for acute myocardial infarction (AMI). Although its primary success rate is well documented, the frequency of restenosis after this procedure is unclear. The frequency of restenosis was determined in patients undergoing emergency PTCA at least 6 months after PTCA was performed during AMI. Of 66 consecutive patients undergoing emergency PTCA, 25 had a second, elective catheterization at an average of 22 months after AMI and 6 underwent repeat catheterization because of recurrent chest pain. Restenosis of the PTCA site was found in 10 of the 31 patients (32%) restudied. Also, 14 (45%) of these 31 patients showed progression of narrowing in the non-infarct-related coronary arteries. In summary, patients in whom AMI is treated by PTCA are at risk for restenosis and for progressive narrowing of the non-infarct artery.

Angioplasty, Balloon↗
PubMed1987

Assessment of residual coronary arterial stenosis after thrombolytic therapy during acute myocardial infarction.

Maximal myocardial salvage appears to be related to the severity of residual coronary arterial stenosis after thrombolysis. The degree of residual infarct vessel stenosis was assessed in 119 consecutive patients with patent arteries who received streptokinase during acute myocardial infarction. After administration of streptokinase, 99 of 119 patients (83%) had a residual stenosis 70% or more in diameter. Assuming that a residual diameter stenosis of at least 70% is flow limiting, the feasibility for percutaneous transluminal coronary angioplasty (PTCA) was determined by the following criteria: length less than 10 mm, no significant distal narrowing or left main stenosis, and an adequate-sized distal artery. In 81 of 99 patients (82%), arterial anatomy was suitable for PTCA. Thus, after therapy with streptokinase for acute myocardial infarction, most patients have a significant infarct arterial residual stenosis and are candidates for PTCA.

Aged↗
PubMed1987

Metabolic support during coronary reperfusion.

The limitation of infarct size by thrombolysis could potentially be improved by an early metabolic intervention. We therefore evaluated the effects of a 48-hour infusion of glucose-insulin-potassium (GIK) in patients with anterior infarctions. Seventeen patients were randomized to receive intravenous GIK (n = 10) or placebo (n = 7). All patients additionally received streptokinase. Changes in left ventricular function were assessed by comparing the global ejection fractions and the regional infarct area ejection fractions of the first ventriculogram with the 10-day second ventriculogram. There was a significantly greater improvement in the global ejection fraction of patients receiving GIK (increases 0.07 +/- 0.04) than in those randomized to placebo (decreases 0.08 +/- 0.04) (p less than 0.02). There was also a much greater improvement in the area ejection fractions of the group receiving GIK vs the group receiving placebo in the anterolateral (increases 0.24 +/- 0.07 vs decreases 0.02 +/- 0.04 [p less than 0.02]) and diaphragmatic (increases 0.08 +/- 0.08 vs decreases 0.17 +/- 0.05 [p less than 0.005]) segments. Thus in patients with anterior infarctions receiving streptokinase, GIK improves ventricular function and reduces the size of the segmental wall motion abnormality.

Adult↗
PubMed1987

Three year anatomic, functional and clinical follow-up after successful percutaneous transluminal coronary angioplasty.

Because the long-term anatomic effects of percutaneous transluminal coronary angioplasty are unknown, follow-up evaluations including coronary angiography, treadmill exercise testing and rest and bicycle exercise radionuclide angiography were performed in 46 patients 6.3 +/- 2.0 and 37.6 +/- 3.6 (mean +/- SD) months after they had undergone successful single lesion angioplasty. The severity of the coronary stenosis decreased significantly at each evaluation; the mean diameter stenosis was 66 +/- 13% before angioplasty, 30 +/- 13% immediately after and 26 +/- 16% and 19 +/- 13% at 6 months and 3 years, respectively. Exercise time increased from 9.8 +/- 4.4 minutes before angioplasty to 18.3 +/- 4.5 minutes immediately after the procedure and remained at that level at 6 months (20.3 +/- 4.6 minutes) and 3 years (18.2 +/- 4.5 minutes). Left ventricular ejection fraction during exercise decreased 4 +/- 6% compared with rest before angioplasty, but increased 7 +/- 7% immediately after angioplasty and this increase was maintained at 6 months (+/- 6 +/- 7%) and 3 years (+/- 4 +/- 6%). Before angioplasty, 1 patient was in Canadian Heart Association functional class 0, 15 were in class II, 24 in class III and 6 in class IV. Three years later, 25 were in class 0, 10 in class I, 7 in class II and 4 in class III. These results indicate that the short-term anatomic and functional success of coronary angioplasty is maintained for at least 3 years.

Adult↗
PubMed1987

Quantitation of ischemia during total coronary occlusion with computer-assisted high resolution ST-segment monitoring: effect of collateral flow.

The effect of increasing grades of collateral flow to the distal target vessel on the clinical and electrocardiographic manifestations of ischemia was evaluated in 118 patients undergoing transluminal coronary angioplasty (TCA). A qualitative scoring system for collateralization was defined as follows: 0--no visible collaterals; 1--visualization of collateral vessels only with no filling of the distal TCA vessel; 2--partial filling of the distal TCA vessel, and; 3--complete filling of the distal TCA vessel. All patients underwent computerized ST-segment monitoring using 3-channel Holter recorders. Criteria for an ischemic ST-segment response was 1.0 mm ST-segment deviation from ST baseline measured 60 msec after the J-point. Episodes of chest pain during and after the procedure were noted. Patients with collateral filling (collateral scores 2 and 3) of the distal TCA vessel had a significantly decreased incidence of angina and diagnostic ischemic ST-segment changes (42% and 15% respectively) as compared to patients without collateral filling (collateral scores 0 and 1) (83% and 74%) (p less than .001). Fifty-eight percent of patients without collateral filling had ischemic ST-segment responses on every balloon inflation as opposed to only 9% with collateral filling (p less than .0001). After TCA, the incidence of angina and ischemic ST-segment changes was similar in both groups (20% and 17% without collateral filling vs. 9% and 9%). We conclude that: 1. increasing qualitative collateralization protects against the development of myocardial ischemia during TCA, but; 2. the similar incidence of late episodes of ischemia after successful TCA suggests that collateral flow may no longer be adequate.

Angioplasty, Balloon↗