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Biomedical subjects

M J Kern

Publications and source records attributed to M J Kern.

At least 199 records · Page 11Linked to original sources
PubMed1993

Race and prognosis after myocardial infarction. Results of the thrombolysis in myocardial infarction (TIMI) phase II trial.

BACKGROUND: To better understand the role of race/ethnicity in survival after acute myocardial infarction, we compared clinical and laboratory data, response to thrombolytic therapy, and clinical outcome in 2885 patients participating in the Thrombolysis in Myocardial Infarction Phase II (TIMI II) Trial among three groups of patients (2564 whites, 174 blacks, and 147 Hispanics). METHODS AND RESULTS: Differences were found in baseline characteristics among the three groups including (1) age (mean age for whites, 57.2 years; blacks, 54.8 years; Hispanics, 52.8 years; P < .001), (2) sex (percentage of women for whites, 17.6; blacks, 28.7; Hispanics, 14.3; P < .001), and (3) risk factor prevalence: current smoking (percent for whites, 49.4; blacks, 62.1; Hispanics, 55.1; P < .003), history of hypertension (percent for whites, 36.6; blacks, 55.7; Hispanics, 39.5; P < .001), and diabetes mellitus (percent for whites, 11.9; blacks, 22.4; Hispanics, 19.7; P < .001). Changes in hemostatic factors 5 hours after infusion of recombinant tissue plasminogen activator (rt-PA) revealed a more profound fall in fibrinogen levels in black patients compared with the response seen in Hispanic or white patients (mean change in fibrinogen +/- SD, mg/dL: 151.3 +/- 107.4, 112.2 +/- 97.0, 109.4 +/- 98.6; P < .001, respectively) without more frequent infarct-related artery patency or hemorrhagic complications. Mortality was similar in the white, black, and Hispanic patients through the first year after adjustment for baseline variables. CONCLUSIONS: TIMI II data yield evidence that (1) corroborates published reports of a high prevalence of classic cardiovascular risk factors among minority patients with acute myocardial infarction, (2) there is a greater decrease in fibrinogen levels 5 hours after the start of rt-PA infusion among black patients than in white and Hispanic patients without evidence of more frequent infarct-related artery patency or hemorrhagic complications, and (3) thrombolytic therapy with appropriate supplemental measures is associated with comparable 1-year mortality in white, black, and Hispanic patients.

Black or African American↗
PubMed1993

Comparison of phasic blood flow velocity characteristics of arterial and venous coronary artery bypass conduits.

BACKGROUND: Coronary artery bypass conduits derived from internal mammary arteries show relative resistance to atherosclerosis and significantly improved long-term patency compared with saphenous vein grafts. Atherothrombotic occlusion of venous conduits has previously been correlated with lower flow rates measured intraoperatively. To quantitate coronary bypass conduit flow velocity, we examined the phasic blood flow velocity patterns by intravascular Doppler spectral analysis in patients during cardiac catheterization to test the hypothesis that resting systolic and diastolic phasic blood flow velocity patterns differ significantly between arterial and venous bypass conduits. METHODS AND RESULTS: Spectral phasic blood flow velocity was measured using an intravascular Doppler-tipped angioplasty guidewire in the proximal, mid, and distal segments of 18 internal mammary artery conduits and 11 saphenous vein grafts in 27 patients at a mean of 4 years (range, 1 to 11) postoperatively. In situ internal mammary artery conduits demonstrated a gradual longitudinal transition in the phasic flow pattern from predominantly systolic velocity proximally (diastolic/systolic peak velocity ratio, 0.6 +/- 0.2) to predominantly diastolic velocity distally (diastolic/systolic peak velocity ratio, 1.4 +/- 0.3; P < .001). Saphenous vein graft flow velocity pattern, however, showed a consistently diastolic predominance, both proximally and distally (diastolic/systolic peak ratios, 1.4 +/- 0.6 and 1.5 +/- 0.7, respectively; P = NS). Mean flow velocities, total velocity integral, and calculated maximal shear rates were significantly higher in all segments of internal mammary arteries compared with values in saphenous vein grafts. CONCLUSIONS: Patterns of resting phasic blood flow, as well as mean velocity and total velocity integral, differ significantly between internal mammary artery and saphenous vein bypass conduits. These differences may have implications regarding blood-vessel wall interactions, the development of degenerative graft disease, and long-term conduit patency.

Blood Flow Velocity↗
PubMed1992

Use of intracoronary ultrasonography in assessing pharmacotherapy for myocardial ischemia.

Intracoronary ultrasonography can provide morphologic and physiologic information on coronary vasomotor responses to pharmacotherapy. Preliminary studies indicate a high correlation between dimensions determined by 2-dimensional echocardiography, angiography, and pathology. Similarly, the emerging data on intracoronary Doppler flow velocity responses beyond atherosclerotic obstructions before, during, and after coronary balloon occlusion will provide further insights into myocardial oxygen supply and its responses to pharmacotherapy during controlled myocardial ischemia.

Coronary Circulation↗
PubMed1992

A novel murine homeobox gene isolated by a tissue specific PCR cloning strategy.

We have identified a novel homeobox gene, designated K-2, using a reverse transcription PCR cloning strategy. Sequence analysis reveals that the homeobox of K-2 is 77.6% homologous at the nucleotide level and 97% identical at the amino acid sequence level to another murine gene, S8. Homeodomain sequence comparisons indicate that K-2 and S8 represent a distinct subclass of paired type homeobox genes. Northern blot analysis of RNA from murine embryos and adult tissues identified multiple transcripts that are expressed in a developmentally specific and tissue restricted manner. Alternate splicing of K-2 at the 3-coding region leads to the inclusion of a chain terminating sequence. In addition, the developmental expression pattern of this gene at day 12 of gestation was determined by in situ hybridization. Expression was observed in diverse mesenchymal cells in craniofacial, pericardial, primitive dermal, prevertebral, and genital structures.

Alternative Splicing↗
PubMed1992

Perspective: the cellular influences of calcium antagonists on systemic and coronary hemodynamics.

Calcium antagonists may have a valuable role in ameliorating the extent and duration of myocardial ischemia following infarction. The precise cellular effects of these agents are being revealed through studies using the model of transient coronary occlusion induced by coronary angioplasty. The class of calcium antagonists is not uniform, and these diverse agents may have a favorable effect on ischemia through one or more of the following mechanisms: direct cardioprotective effects, prevention of calcium accumulation in the mitochondria in ischemic cells, reduction in oxygen consumption or in coronary artery vasoconstriction or coronary spasm, prevention of ischemia-induced arrhythmias, and increased coronary blood flow to ischemic tissue directly or through enhancement of collateral flow. Recent studies of diltiazem, nifedipine, nicardipine, nisoldipine, and amlodipine, as representative agents, are reviewed.

Animals↗
PubMed1992

Advisory group reports on silent myocardial ischemia, acute intervention after myocardial infarction, and postinfarction management.

Three advisory groups of the Council for Myocardial Ischemia and Infarction regularly review current knowledge concerning the following clinical contexts: silent ischemia, acute intervention, and postmyocardial infarction. This article represents the most recent findings of each Advisory Group--the areas of agreement and those of disagreement. What is emphasized here is that ongoing research is critical to refining the therapeutic approach to ischemia and the postmyocardial infarction patient. What seems rational is the stratification of patients into risk groups--high and low--that dictate whether intervention should be aggressive or conservative.

Algorithms↗
PubMed1992

Interpretation of cardiac pathophysiology from pressure waveform analysis: coronary hemodynamics: I. Coronary catheter pressures.

The coronary pressure waveforms described in this rounds are an integral part of the angiographers approach to all patients, especially those with suspected left main coronary stenosis. Patient management will differ according to the laboratory experience and training of the operators. Recognition and appreciation of abnormal coronary pressure waveforms may directly affect the life and death of these patients.

Blood Pressure↗
PubMed1992

Interpretation of cardiac pathophysiology from pressure waveform analysis: coronary hemodynamics. Part II: Patterns of coronary flow velocity.

These specialized tracings illustrate several important patterns of coronary blood flow velocity that may occur in patients during diagnostic cardiac catheterization. Recent advances in catheter methodologies permit easy measurement of coronary blood flow during routine coronary angiography. At the current time, measurement of coronary blood flow velocity remains a research technique but is of continuing interest in clinical syndromes of atypical angina, myocardial hypertrophy and infarction, early transplant rejection, or premature (subangiographic) atherosclerosis in some patients. A later hemodynamic rounds will examine the effects of coronary blood flow velocity and various hyperemic stimuli to assess coronary vasodilatory reserve.

Atrial Fibrillation↗
PubMed1992

Angiographic identification of malpositioned balloon catheters during mitral valvuloplasty.

The positioning of balloon catheters for the percutaneous mitral valvuloplasty technique is critical to ensure an adequate result and minimize complications. Passage of two balloon catheters in parallel through a thickened atrial septum and maintenance of satisfactory positioning in the left ventricle can be difficult. We describe unsuspected malpositioning of the balloons in two patients documented angiographically in our laboratory. Recognizing and avoiding these positions will reduce the potential for serious complications.

Adult↗
PubMed1992

Interpretation of cardiac pathophysiology from pressure waveform analysis: effects of nitroglycerin.

Nitroglycerin has dependable, short-lived veno- and arterial vasodilatory effects ameliorating ischemia through both preload reduction and coronary vasodilation. Nitroglycerin should be used prior to left ventriculography in patients with elevated left ventricular end-diastolic pressure. The arterial pressure waveform alteration of nitroglycerin can be explained on the basis of changes in arterial distensibility and reflected wave patterns and may vary considerably among individuals with different degrees of atherosclerosis.

Aged↗
PubMed1992

Interpretation of cardiac pathophysiology from pressure waveform analysis: pericardial compressive hemodynamics, Part II.

Constrictive physiology characteristically alters atrial and ventricular waveforms. Normal pressure and flow responses to inspiration are blocked or reversed. The impairment of early diastolic filling is the common feature of restrictive myocardial, as well as diseased pericardial, processes. Low pressure tamponade can limit cardiac output, but may be difficult to detect by clinical signs alone. Examination of the pressure waveforms may provide clues to the diagnosis of constrictive physiology in these patients.

Blood Pressure↗
PubMed1992

Interpretation of cardiac pathophysiology from pressure waveform analysis: pericardial compressive hemodynamics, Part III.

Failure of right atrial pressure to normalize after pericardial pressure is relieved suggests persistent effusive-constrictive physiology, myocardial failure, or cardiomyopathy which may have indistinguishable hemodynamic pressure waveforms. Clinical characteristics, ancillary testing, and endomyocardial biopsy may be required to obtain a definite diagnosis in such cases. The hemodynamic waveforms obtained during pericardiocentesis provide insight into the pathophysiologic processes, producing symptoms of dyspnea in this interesting patient group.

Adult↗
PubMed1992

Interpretation of cardiac pathophysiology from pressure waveform analysis: coronary hemodynamics, Part III: Coronary hyperemia.

Basal patterns (systolic/diastolic components) of coronary flow velocity as previously described are generally maintained during hyperemia and can be easily recorded in the catheterization laboratory during pharmacologic stimulation. The interpretation of the clinical significance of coronary vasodilatory reserve may be complicated by both coronary and myocardial diseases. Distal coronary artery hyperemic responses measured with ultrasound Doppler-tipped guidewires will provide new information on traditional observations of coronary physiology in humans.

Adenosine↗