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Biomedical subjects

M J Kern

Publications and source records attributed to M J Kern.

At least 163 records · Page 9Linked to original sources
PubMed1994

Continuous coronary flow velocity monitoring during coronary interventions: velocity trend patterns associated with adverse events.

Continuous measurement of blood flow velocity during interventional procedures has the potential to provide an early warning of coronary flow instability, which can lead to abrupt closure or other adverse events before angiography. The magnitude and fluctuations of the average velocity over time (trend) was studied by using a 0.018-inch Doppler-tipped angioplasty guide wire in 32 patients after coronary angiography (n = 20), atherectomy (n = 2), urgent stent (n = 6), urgent vein graft thrombolysis (n = 4), or acute myocardial infarction (n = 2). The patients (mean age 60 +/- 11 years) had postprocedural in-laboratory flow monitoring for a mean of 19 +/- 11 (range 8 to 36) minutes. The coronary artery monitored was the left anterior descending in 13, circumflex in 6, right coronary artery in 9, and saphenous vein graft in 4. Seven patients had flow-related events during continuous flow velocity monitoring before serial angiographic study. These events included coronary vasospasm (abrupt flow acceleration), vasovagal flow cessation, cyclical flow variations resulting from accumulation of intraluminal thrombus, and rapid decline of flow velocity. The last two patterns were associated with abrupt vessel closure during angioplasty. Continuous flow velocity monitoring is easily incorporated into routine interventional procedures and provides an early indication of unstable flow and the potential for abrupt vessel closure and other adverse events.

Adult↗
PubMed1994

Intraaortic balloon pump support during high-risk coronary angioplasty.

Intraaortic balloon pump support has been demonstrated to be of clinical benefit when used therapeutically and prophylactically in high-risk patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Afterload reduction and post-PTCA-enhanced coronary blood flow afforded by diastolic augmentation during intraaortic balloon pumping provides hemodynamic stabilization, attenuates clinical perturbations of myocardial ischemia, and may provide an important 'bridge' to emergent coronary bypass surgery following abrupt vessel closure complicating PTCA. Recent studies demonstrate a reduction in cardiac morbidity and improved coronary artery patency among patients receiving prophylactic intraaortic balloon pumping after establishing infarct artery reperfusion during acute cardiac catheterization for acute myocardial infarction. A modest increase in cardiac output (20-30%), the requirement of a stable, regular cardiac rhythm, peripheral vascular disease and aortic insufficiency limits the use of intraaortic balloon pump support in relatively few patients. These studies demonstrate that intraaortic balloon counterpulsation provides an effective and safe form of mechanical support in many high-risk patients undergoing PTCA.

Angioplasty, Balloon, Coronary↗
PubMed1994

Correlation of pharmacological 99mTc-sestamibi myocardial perfusion imaging with poststenotic coronary flow reserve in patients with angiographically intermediate coronary artery stenoses.

BACKGROUND: The physiological assessment of angiographically intermediate-severity stenoses remains problematic. Functional measurements of poststenotic intracoronary Doppler coronary flow reserve can be performed in humans but have not been correlated with hyperemic myocardial perfusion imaging or angiographic data in this patient population. METHODS AND RESULTS: Thirty-three patients undergoing diagnostic quantitative coronary angiography (QCA) for assessment of intermediate-severity coronary artery disease (mean QCA percent diameter stenosis, 56 +/- 14%) were studied. Proximal and distal poststenotic Doppler coronary flow velocities were measured (left anterior descending coronary artery, 16; right coronary artery, 10; left circumflex artery, 7 patients) before and during peak maximal hyperemia with intracoronary adenosine (8 to 12 micrograms). Intravenous pharmacological stress (adenosine, 20 patients; dipyridamole, 13 patients) 99mTc-sestamibi tomographic perfusion imaging was performed within 1 week of coronary flow-velocity studies. kappa statistics were calculated to measure the strength of correlation among coronary flow velocities, perfusion imaging data, and QCA results. QCA stenosis severity (abnormal, > or = 50% diameter stenosis) and poststenotic Doppler coronary flow reserve (ratio of abnormal distal hyperemic to basal flow, < or = 2.0) were correctly correlated in 20 of 27 patients (74%; kappa = .48). QCA stenosis severity and 99mTc-sestamibi imaging (abnormal if one or more reversible myocardial segments were present in the poststenotic zone) were correlated in 28 of 33 patients (85%; kappa = .63). 99mTc-sestamibi imaging results agreed with the basal (nonhyperemic) proximal-to-distal velocity ratio (normal, < 1.7) in 15 of 31 patients (48%; kappa = .17). The strongest correlation occurred between hyperemic distal flow-velocity ratio measurements and 99mTc-sestamibi perfusion imaging results in 24 of 27 patients (89%; kappa = .78). All 14 patients with abnormal distal hyperemic flow-velocity values had corresponding reversible 99mTc-sestamibi tomographic defects. More reversibly hypoperfused segments were present in patients with abnormal poststenotic hyperemic flow-velocity ratios (abnormal, 2.4 +/- 0.7 segments; normal, 0.6 +/- 1.0 segments; P < .05). The number of poststenotic myocardial 99mTc-sestamibi perfusion defects was correlated with the QCA percent cross-sectional area reduction (P < .02) and with minimal luminal diameter (P < .05) of intermediate-severity coronary artery stenoses. CONCLUSIONS: Two technologically diverse functional measures of stenosis severity--Doppler-derived poststenotic hyperemic intracoronary flow reserve and vasodilator stress 99mTc-sestamibi myocardial perfusion imaging--are highly (89%) correlated. The physiological assessment of coronary stenoses of angiographically intermediate severity may be improved by the use of these techniques.

Adenosine↗
PubMed1994

Impact of age on clinical outcome and postlytic management strategies in patients treated with intravenous thrombolytic therapy. Results from the TIMI II Study. TIMI II Investigators.

BACKGROUND: Few thrombolytic studies have assessed whether patient age is an indication for routine postlytic cardiac catheterization and revascularization or evaluated the impact of age on 1-year outcome differences after acute myocardial infarction. METHODS AND RESULTS: A secondary analysis of 3339 patients enrolled in the TIMI II trial was performed to identify differences in clinical and coronary angiographic findings and 1-year cardiac event rates among 841 patients < 50 years old, 1639 patients 50 to 64 years old, and 859 patients 65 to 75 years old. Differences in 1-year clinical outcome were assessed among patients randomly assigned to an invasive or a conservative postlytic strategy within each age group. The percentages of patients with a prior history of myocardial infarction, angina, congestive heart failure, hypertension, or diabetes mellitus or an infarction complicated at the time of study entry by shock, pulmonary edema, hypotension, rales more than one third of lung fields, or atrial fibrillation as well as the percentage of female patients (all P < .001) increased with age. Fewer older patients (65 to 75 years) received early (ie, < or = within 2 hours after symptom onset) treatment with recombinant tissue-type plasminogen activator (rTPA), and fewer were eligible for random assignment to immediate or deferred beta-blocker therapy (P = .01). The location of the infarct-related artery and the percentage of patients with patent (ie, TIMI flow grade 2 or 3) or "complete" (ie, TIMI flow grade 3) infarct-related artery flow did not vary with age. The percentage of patients with multivessel disease was greatest in the older patients (P = .001). Cumulative 1-year mortality was low in the youngest patients (2.8%; 99% confidence interval [CI], 1.6% to 4.7%) regardless of whether the infarct location was anterior (3.7%) or nonanterior (1.6%). The highest 1-year mortality occurred in the older patients (13.6%; 99% CI, 10.9% to 16.9%), particularly when the infarct location was anterior (18%). The 42-day rates of reinfarction (P = .85), death (P = .95), or death or reinfarction (P = .99) were similar in patients assigned to the invasive or conservative postlytic treatment strategy, regardless of age group. CONCLUSIONS: Among patients with acute myocardial infarction treated with intravenous rTPA, heparin, and aspirin, there were age-related differences in time to treatment with thrombolytic therapy, use of beta-blockers, extent of coronary artery disease, and 1-year cardiac event rates. Routine use of cardiac catheterization and coronary revascularization does not improve immediate or 1-year outcome in terms of mortality or reinfarction compared with a more conservative strategy in young, middle-aged, or elderly patients similar to those enrolled in TIMI II.

Adult↗
PubMed1994

Use of aortic counterpulsation to improve sustained coronary artery patency during acute myocardial infarction. Results of a randomized trial. The Randomized IABP Study Group.

BACKGROUND: Aortic counterpulsation has been observed to reduce the rate of reocclusion of the infarct-related artery after patency has been restored during acute myocardial infarction in observational studies. To evaluate the benefit-to-risk ratio of aortic counterpulsation during the early phase of myocardial infarction, a multicenter randomized clinical trial was performed. METHODS AND RESULTS: Patients who had patency restored during acute cardiac catheterization within the first 24 hours of onset of myocardial infarction were randomly assigned to aortic counterpulsation for 48 hours versus standard care. Intravenous heparin was used similarly in both groups and was continued for a median (25th, 75th percentile) of 5 (2,7) days. A total of 182 patients were enrolled; 96 were assigned to aortic counterpulsation and 86 to standard care. Repeat cardiac catheterization was performed at a median of 5 (4,6) days after randomization in 89% of patients assigned to aortic counterpulsation and in 90% of control patients. Patients randomized to aortic counterpulsation had similar rates of severe bleeding complications (2% versus 1%), number of units of blood transfused (mean, 1.3 +/- 2.6 versus 0.9 +/- 1.8 units), and vascular repair or thrombectomy (5% versus 2%) compared with patients treated in a conventional manner. Patients randomized to aortic counterpulsation had significantly less reocclusion of the infarct-related artery during follow-up compared with control patients (8% versus 21%, P < .03). In addition, there was a significantly lower event rate in patients assigned to aortic counterpulsation in terms of a composite clinical end point (death, stroke, reinfarction, need for emergency revascularization with angioplasty or bypass surgery, or recurrent ischemia): 13% versus 24%, P < .04. CONCLUSIONS: This randomized trial showed that careful use of prophylactic aortic counterpulsation can prevent reocclusion of the infarct-related artery and improve overall clinical outcome in patients undergoing acute cardiac catheterization during myocardial infarction.

Angioplasty, Balloon, Coronary↗
PubMed1993

Effects of percutaneous transluminal coronary angioplasty balloon compliance on angiographic and clinical outcomes.

The effect of balloon compliance on the safety and outcome of percutaneous transluminal coronary angioplasty (PTCA) is controversial. It has been proposed that PTCA balloons constructed from compliant polymers contribute to an increased risk of angiographic coronary dissection and potentially to adverse clinical results. To determine the effect of balloon material compliance on PTCA outcome, 1,076 PTCA procedures using balloons differing in compliance characteristics (polyethylene teraphthalate [noncompliant], polyethylene [intermediately compliant] or polyolefincopolymer [compliant]) were retrospectively analyzed. Baseline clinical, angiographic and procedural variables were similar among the 3 balloon material groups. In the noncompliant, intermediately compliant and compliant groups, the occurrence rates of intimal tears (10, 14 and 10%, respectively; p = NS for all comparisons) and coronary dissection (7, 9 and 8%, respectively; all p = NS) were also equivalent. The rates of acute occlusion, myocardial infarction, emergency bypass surgery and death were low and similar, and likewise unaffected by balloon material. The results provide evidence that the occurrence of adverse outcomes after PTCA is unrelated to balloon material compliance and support the clinical safety of balloons constructed of compliant or noncompliant polymers when used for appropriate coronary interventions.

Angioplasty, Balloon, Coronary↗
PubMed1993

Coronary flow velocity dynamics in normal and diseased arteries.

Distal coronary flow velocity measurements were previously limited to open heart or experimental procedures. Unlike previous Doppler catheter techniques, a Doppler angioplasty flow wire permits flow velocity measurements in both the proximal and distal segments of normal and diseased coronary arteries. In order to determine the potential clinical application of the Doppler flow wire, we performed baseline and hyperemia flow velocity measurements in proximal and distal segments of 20 angiographically normal arteries (right coronary = 8; left circumflex = 7; left anterior descending = 5) and 29 significantly stenosed arteries. All 3 normal coronary arteries had a diastolic-predominant pattern in both proximal and distal segments; the right coronary artery showed significantly less diastolic predominance. The coronary vasodilator reserve was similar in all three normal coronary arteries, and in the proximal and distal arterial segments. Abnormal arteries had significantly lower coronary vasodilator reserve (normal vs abnormal, 2.3 +/- 0.8/1.6 +/- 0.7; p < 0.02). Normal arteries had preservation of velocity parameters in the distal segments; abnormal arteries had a significant decrease in distal velocity parameters. The proximal-to-distal velocity ratio was thus significantly higher in abnormal arteries (2.4 +/- 0.7 vs 1.1 +/- 0.2; p < 0.001). The coronary vasodilator reserve in proximal and distal arteries--in addition to the proximal to distal velocity ratio--may provide functional and hemodynamic data complementary to coronary angiography in the assessment of coronary artery stenosis.

Blood Flow Velocity↗
PubMed1993

Assessment of angiographically intermediate coronary artery stenosis using the Doppler flowire.

Determination of the clinical and hemodynamic significance of coronary stenoses is often difficult and inexact. Angiography and coronary vasodilator reserve have been shown to be imperfect tools to determine the physiologic significance of coronary stenoses. Spectral flow velocity data, both proximal and distal to coronary stenoses, using an 0.018-in intracoronary Doppler-tipped angioplasty guidewire, were compared to translesional pressure gradients and angiography during cardiac catheterization. Patients were divided into 2 groups based on resting translesional gradients: Group 1 had gradients < 20 mm Hg and group 2 had gradients > or = 20 mm Hg. Proximal average peak velocity, diastolic velocity integral, and total velocity integral were statistically significantly lower in Group 1. The distal average peak velocity, and diastolic and total velocity integrals were all significantly (p < 0.01) decreased in patients with gradients > 20 mm Hg (group 2). The ratio of proximal-to-distal total flow velocity integral was also higher in group 2 patients (2.3 +/- 0.9) compared with group 1 (1.1 +/- 0.2; p < 0.001). There was a strong correlation between translesional pressure gradients and the ratios of the proximal-to-distal total flow velocity integrals (r = 0.8, p < 0.001) with a weaker relationship between quantitative angiography and pressure gradients (r = 0.6, p < 0.001). Angiography was a poor predictor of translesional gradients in angiographically intermediate stenoses (range 50-70%; r = 0.2, p = NS), while the flow velocity ratios continued to have a strong correlation (r = 0.8, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Quantitating coronary collateral flow velocity in patients during coronary angioplasty using a Doppler guidewire.

Quantitation of coronary collateral flow in patients has been limited to angiographic techniques, which are subject to well-known methodologic limitations. The use of a Doppler-tipped angioplasty guidewire permits measurement of both antegrade and retrograde flow distal to totally or subtotally occluded vessels that may be supplied with acutely recruitable or angiographically mature collateral conduits. Using coronary flow velocity as an indicator of collateral flow, retrograde flow velocity was quantitated in 17 patients. Mean collateral flow velocity was approximately 30% of normal postangioplasty antegrade flow velocity. The phasic pattern of collateral flow was highly variable, but the retrograde diastolic and systolic flow velocity integrals were 20% and 40% (respectively) of post-procedure antegrade flow velocity. Preliminary studies with pharmacologic stimulation of the contralateral supply artery suggests that collateral flow is not increased by intracoronary nitroglycerin (200 micrograms) or adenosine (12 micrograms), but may be markedly augmented during mechanical stimulation of balloon occlusion. These data represent the first in a series of quantitative observations on control of the coronary collateral circulation in humans. Future investigations using the Doppler Flowire (Cardiometrics) will enhance understanding of factors modulating ischemia through collateral supply.

Angioplasty, Balloon, Coronary↗
PubMed1993

Interpretation of cardiac pathophysiology from pressure waveform analysis: simultaneous left and right ventricular pressure measurements.

In addition to demonstrating constrictive and restrictive cardiac physiology, simultaneous right and left ventricular pressure measurements can be helpful to identify various aspects of myocardial dysfunction. Intracardiac conduction defects will displace the right ventricular pressure under the left ventricular pressure upstroke and identify differences in the timing of ventricular contraction. Right ventricular dysfunction will also produce abnormal right ventricular pressure waveforms which may overlap left ventricular pressure and contribute to abnormalities in right atrial and ventricular pressure waveforms.

Adult↗
PubMed1993

Examination of the effects of hemodynamic and pharmacologic interventions on coronary collateral flow in a patient during cardiac catheterization.

The vasomotor response of native human collateral vessels to pharmacologic or hemodynamic vasodilatory stimuli is not well known. We describe a case where retrograde collateral flow velocity was measured both at baseline and following selected hemodynamic and pharmacologic interventions. This index case represents the first in a series of potential human physiologic studies designed to address questions pertaining to control of collateral blood supply in humans.

Adenosine↗
PubMed1993

Interpretation of cardiac pathophysiology from pressure waveform analysis: multivalvular regurgitant lesions.

Multivalvular regurgitant lesions may have a common etiology, such as an underlying connective tissue disorder, Marfan's disease or cardiomyopathy. Careful collection of routine simultaneous left and right heart hemodynamics will document the individual valvular lesions. Combined echocardiography and angiographic data will further support the interpretation of the hemodynamic waveforms. Clinical decisions for valve repair or replacement will be based on the severity of associated lesions, myocardial function and other patient specific characteristics [9] indicating the acceptable limits of surgical risk.

Cardiac Catheterization↗
PubMed1993

Superior accuracy of anatomic positioning with echocardiographic- over fluoroscopic-guided endomyocardial biopsy.

To assess the superior anatomic positioning of echocardiographic-guided endomyocardial biopsy compared to traditional fluoroscopic-guided technique, these two modalities were compared in a blinded fashion during femoral sheath endomyocardial biopsy in 21 patients, 19 being evaluated after orthotopic cardiac transplantation. The simultaneous fluoroscopic and echocardiographic imaging indicated that traditional fluoroscopic positioning of the bioptome against the septum is inaccurate in over half of patients undergoing biopsy. This finding should be considered in cardiomyopathy patients or those at high risk for biopsy-related complications.

Biopsy↗