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Biomedical subjects

Walter A Parham

Publications and source records attributed to Walter A Parham.

8 recordsLinked to original sources
PubMed2006

Hyperkalemia revisited.

Hyperkalemia is a common clinical condition that can induce deadly cardiac arrhythmias. Electrocardiographic manifestations of hyperkalemia vary from the classic sine-wave rhythm, which occurs in severe hyperkalemia, to nonspecific repolarization abnormalities seen with mild elevations of serum potassium. We present a case of hyperkalemia, initially diagnosed as ventricular tachycardia, to demonstrate how difficult hyperkalemia can be to diagnose. An in-depth review of hyperkalemia is presented, examining the electrophysiologic and electrocardiographic changes that occur as serum potassium levels increase. The treatment for hyperkalemia is then discussed, with an emphasis on the mechanisms by which each intervention lowers serum potassium levels. An extensive literature review has been performed to present a comprehensive review of the causes and treatment of hyperkalemia.

Aged↗
PubMed2004

Lack of relation between imaging and physiology in ostial coronary artery narrowings.

This study compared ostial lesion angiographic severity with physiologic assessment and showed that, for diameter narrowings >70%, fractional flow reserves were >0.75 in 20 of 25 lesions and >0.75 in 30 of 30 lesions with <70% diameter narrowings. Using fractional flow reserve in all ostial narrowings > or =70% may prevent patients from undergoing unnecessary interventions.

Adenosine↗
PubMed2004

Coronary hyperemic dose responses of intracoronary sodium nitroprusside.

BACKGROUND: Sodium nitroprusside is one of several agents considered effective for treating the no-reflow phenomenon during acute coronary interventions. However, the coronary hyperemic dose responses and systemic hemodynamic effects of intracoronary nitroprusside have yet to be determined in humans. The purpose of this study was to compare the hyperemic and hemodynamic responses of intracoronary nitroprusside to intracoronary adenosine in patients during cardiac catheterization with angiographically normal anterior descending arteries. METHODS AND RESULTS: In 21 patients, coronary blood flow velocity (0.014-inch Doppler flow wire), heart rate, and blood pressure were measured in unobstructed left anterior descending coronary arteries at rest, after intracoronary adenosine (30- to 50-microg boluses), and after 3 serial doses (0.3-, 0.6-, and 0.9-microg/kg boluses) of intracoronary nitroprusside. Coronary reserve was calculated as hyperemia/basal coronary flow velocity. In an additional 9 patients with intermediate stenoses (53+/-7%), 14 fractional flow reserve (FFR) measurements (using 0.014-inch pressure wire) were performed with both intracoronary adenosine and nitroprusside (0.6 microg/kg). Intracoronary nitroprusside produced equivalent coronary hyperemia with a longer duration ( approximately 25%) compared with intracoronary adenosine. Intracoronary nitroprusside (0.9 microg/kg) decreased systolic blood pressure by <20%, with minimal change in heart rate, whereas intracoronary adenosine had no effect on these parameters. FFR measurements with intracoronary nitroprusside were identical to those obtained with intracoronary adenosine (r=0.97). CONCLUSIONS: Compared with adenosine, intracoronary nitroprusside produces an equivalent but more prolonged coronary hyperemic response in normal coronary arteries. Intracoronary nitroprusside, in doses commonly used for the treatment of the no-reflow phenomenon, can produce sustained coronary hyperemia without detrimental systemic hemodynamics. On the basis of FFR measurements compared with adenosine, sodium nitroprusside also appears to be a suitable hyperemic stimulus for coronary physiological measurements.

Adenosine↗
PubMed2004

The influence of obstructive sleep apnea on FFR measurements for coronary lesion assessment.

Fractional flow reserve (FFR) determinations have been demonstrated to be largely independent of changes in systemic hemodynamic changes. Herein, we describe a case of obstructive sleep apnea cyclically altering FFR measurements from normal to abnormal in a patient with an intermediately severe coronary narrowing following treatment for an acute coronary syndrome. To eliminate uncertainty, FFR measurements should be made if possible during suspended respiration.

Blood Flow Velocity↗
PubMed2003

Management of iliac stent movement complicating peripheral vascular intervention: A rescue technique when stent deployment malfunctions.

Percutaneous transluminal peripheral angioplasty (PTA), with and without stenting, has become an effective, accepted, and safe approach for treating intermittent claudication and critical leg ischemia in selected patients. Percutaneous peripheral interventions are subject to complications that require unique solutions when compared to coronary interventions. We report a case of common iliac artery stenting complicated by stent migration and describe an approach to the management of this problem.

Angioplasty, Balloon↗