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Biomedical subjects

D W Ferguson

Publications and source records attributed to D W Ferguson.

At least 55 records · Page 3Linked to original sources
PubMed1985

Absence of left anterior descending coronary artery associated with anomalous origin of left circumflex coronary artery from the right coronary artery: a case report and review.

In this report we present a case of a 30-year-old female patient with a single coronary artery, which consisted of a right coronary artery from which there was an anomalous origin of the left circumflex coronary artery. There was no left anterior descending coronary artery. The clinical and other noninvasive diagnostic features of this rare angiographic variant are described and compared to other known varieties of coronary anomalies. The absence of objective evidence of ischemia or left ventricular functional impairment and analysis of the angiographic data suggest that this is another benign variant of coronary anatomy.

Adult↗
PubMed1985

Effects of nifedipine on baroreflex modulation of vascular resistance in man.

Studies in animals have demonstrated that, in addition to their vascular effects, calcium channel blockers have important effects on baroreceptor function. We performed a series of experiments to determine if nifedipine, in doses employed clinically, alters baroreflex control of vascular resistance in normal humans. Forearm vasoconstrictor responses of 14 normal subjects to unloading of baroreceptors with lower body negative pressure (LBNP), to a cold pressor test and during intra-arterial infusions of norepinephrine were studied in the control state and following administration of nifedipine. Nifedipine had no effect on baseline mean arterial pressure or central venous pressure. Heart rate and forearm blood flow (FBF) increased significantly following nifedipine: heart rate = 59.7 +/- 2.4 bpm before and 72.6 +/- 4.4 bpm after nifedipine (mean +/- SE, p less than 0.001, n = 14); FBF = 4.6 +/- 0.4 ml X min-1 X 100 ml-1 before and 6.7 +/- 1.0 ml X min1 X 100 ml-1 after nifedipine (p less than 0.02, n = 14). Forearm vascular resistance (FVR) tended to decrease following nifedipine but the difference was not significant: FVR = 21.1 +/- 1.4 units before and 17.8 +/- 2.3 units after nifedipine (p = 0.07, n = 14). Nifedipine attenuated forearm vasoconstrictor responses to cold pressor stimulus: delta FVR during cold pressor test = +10.3 +/- 2.4 units before and +4.7 +/- 1.4 units after nifedipine (p less than 0.02, n = 14). Likewise, nifedipine depressed vasoconstrictor responses to intra-arterial infusion of norepinephrine: delta FVR during norepinephrine = +15.5 +/- 3.4 units before and +10.2 +/- 2.9 units after nifedipine (p less than 0.05, n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Experimental evaluation and initial clinical application of new self-adhesive defibrillation electrodes.

We evaluated the efficacy of self-adhesive electrode pads for defibrillation and cardioversion in animals and patients. In 11 anesthetized dogs, the success rate of shocks given to terminate electrically-induced ventricular fibrillation was similar for both self-adhesive electrode pads and hand-held electrode paddles; success rate approached 100% at energies of 125-150 joules. Eighty patients undergoing defibrillation or elective cardioversion received shocks from self-adhesive pads. In all but 2 patients defibrillation or cardioversion was achieved at least once using these pads. The pads were equally effective from either apex-anterior or apex-posterior positions. The transthoracic impedance using self-adhesive pads was 75 +/- 21 ohms, similar to transthoracic impedance we previously reported when using standard hand-held paddles. No complications occurred with the use of the pads. We conclude that self-adhesive electrode pads are effective for defibrillation and cardioversion.

Animals↗
PubMed1985

Relative contribution of aortic and carotid baroreflexes to heart rate control in man during steady state and dynamic increases in arterial pressure.

We studied the contribution of carotid vs. extracarotid baroreceptors in control of heart rate in normal humans. We measured heart interval (HI) and arterial pressure during steady-state infusion of phenylephrine (PE). PE increased mean arterial pressure (MAP) by 13 +/- 2 mmHg (mean +/- SEM; n = 10) and thus stimulated both carotid and aortic baroreceptors. Neck pressure (NP) was applied during PE infusion to counter the increase in transmural carotid sinus pressure, thus leaving only aortic baroreceptors stimulated by the increase in arterial pressure. PE infusion alone prolonged HI by 230 +/- 24 ms (P less than 0.05). Application of NP attenuated the HI response to 65 +/- 22 ms above control (P less than 0.05 vs. PE alone). During these steady-state increases in arterial pressure, elimination of the carotid baroreflex contribution reduced the HI prolongation by 41-70% in five subjects and by greater than 93% in five subjects. We also measured the HI response to dynamic ramp elevation of systolic arterial pressure (SAP) using bolus administrations of PE. Baroreflex control was calculated from the slope of the regression correlating SAP to succeeding HI for PE alone (carotid and aortic baroreceptor activation) and for PE plus superimposed dynamic NP at levels equal to the increases in SAP (aortic baroreceptor activation). During PE alone, the baroreflex slope was 20.2 +/- 2.9 ms/mmHg (n = 10). During PE plus NP, the baroreflex slope was reduced by 30% to 14.1 +/- 2.8 ms/mmHg (P less than 0.02 vs. during PE alone). Thus, during dynamic increases in arterial pressure, eliminating the carotid baroreflex contribution reduced the HI response by 30%. These studies indicate that extracarotid (presumably aortic) and carotid baroreflexes both participate in control of heart rate in humans. Extracarotid (aortic) baroreflexes appear to have the greater role in control of heart rate during dynamic increases in arterial pressure.

Adult↗
PubMed1984

Influence of baseline ejection fraction and success of thrombolysis on mortality and ventricular function after acute myocardial infarction.

The efficacy of streptokinase (STK) thrombolytic therapy was prospectively evaluated in 77 consecutive patients presenting within 9 hours of onset of acute myocardial infarction. Serial left ventricular (LV) ejection fraction (EF) was assessed by radionuclide ventriculography, initially (acute) and at 1 month (late). The role of initial LVEF was examined by comparing patients with an acute LVEF greater than or equal to 50% (type I) with those with LVEF less than 50% (type II). Sixty-five patients (84%) had total coronary occlusion and received STK. Initial successful reperfusion was achieved in 34 patients (52%), but repeat angiograms at 10 to 14 days revealed persistent patency in only 27 patients. Within the type I and type II classification, 2 patient subgroups were compared: Group A had successful and persistent thrombolysis and group B had initial failure of thrombolysis or in-hospital reocclusion. There was no significant change in global LVEF in any group from acute to 1 month follow-up: group IA--acute EF = 56 +/- 2% (mean +/- standard error of the mean), late EF = 55 +/- 2% (p = not significant [NS]); group IB--acute EF = 58 +/- 1%, late EF = 55 +/- 2% (NS); group IIA--acute EF = 35 +/- 2%, late EF = 4 +/- 4%, (NS); group II B--acute EF = 36 +/- 2%, late EF = 41 +/- 3% (NS). No patient with an acute EF greater than or equal to 50% died, i.e., group IA patients (n = 7) or group IB patients (n = 13).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Systemic markers of fibrinolysis after unsuccessful intracoronary streptokinase thrombolysis for acute myocardial infarction. Does nonreperfusion indicate failure to achieve a systemic lytic state?

Reasons for the failure of intracoronary streptokinase (STK) to result in coronary thrombolysis were examined in 45 patients with acute myocardial infarction presenting with angiographic evidence of total coronary occlusion. In 25 patients (group A), clot lysis was initially successful; in 20 (group B), reperfusion was unsuccessful. The STK dosage in group A ranged from 84,000 to 310,000 units (mean 188,000 +/- 12,000); STK dosage in group B ranged from 160,000 to 360,000 units (mean 267,000 +/- 11,000 [p less than 0.05]). Before therapy, levels of fibrin degradation products and serum fibrinogen were normal in all patients. After intracoronary STK, fibrin degradation products and serum fibrinogen levels changed similarly in both groups. Eight-five percent of patients in group B had evidence of a systemic fibrinolytic state. These data suggest that higher doses of STK administered in the same manner are unlikely to result in an increased reperfusion rate. Systemic hematologic markers of fibrinolysis are not helpful in explaining the success or failure of intracoronary thrombolysis.

Coronary Angiography↗
PubMed1984

Angiographic evidence that reciprocal ST-segment depression during acute myocardial infarction does not indicate remote ischemia: analysis of 23 patients.

Although reciprocal ST-segment depression from the remote noninfarcting ventricular wall during acute myocardial infarction (MI) is a common clinical finding, the significance of this electrocardiographic pattern is unclear. Previous retrospective studies have suggested that these findings may reflect either remote wall ischemia, multivessel coronary artery disease (CAD), extensive MI or a benign electrical phenomenon. Prior studies have lacked angiographic data obtained at the time of these acute electrocardiographic changes. In this study we prospectively evaluated 23 patients with acute MI. Left ventricular wall motion, coronary anatomy and the ECG were all assessed over a short period during the acute phase of the MI. Segmental wall motion was used as a sensitive indicator of ischemia. Seventeen patients had acute anterior MI, of whom 47% had reciprocal ST-segment depression; 6 patients had inferior MI, with 3 showing reciprocal ST depression. The mean degree of ST-segment elevation from the infarcting wall tended to be greater in patients with reciprocal ST-segment depression than in those without such reciprocal ST depression (2.8 +/- 0.4 vs 1.9 +/- 0.3 mm, p = 0.06). Patients with and without reciprocal ST-segment depression had similar degrees of segmental dysfunction in the infarct wall. However, no abnormalities in segmental wall motion in the remote wall were seen regardless of the presence or absence of remote wall ST-segment depression. In addition, the presence or absence of ST-segment depression did not predict the extent or degree of CAD.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Self-adhesive preapplied electrode pads for defibrillation and cardioversion.

The efficacy of self-adhesive electrode pads for defibrillation and cardioversion was assessed in 80 patients who received 267 shocks from self-adhesive pads. In all but two patients, defibrillation or cardioversion was achieved at least once. The pads were equally effective when used in the apex-anterior or apex-posterior position. The transthoracic impedance using self-adhesive pads was 75 +/- 21 ohms (mean +/- standard deviation), which is similar to previously reported transthoracic impedance in defibrillation, using standard hand-held electrode paddles of 67 +/- 36 ohms. It is concluded that self-adhesive electrode pads are effective for defibrillation and cardioversion.

Arrhythmias, Cardiac↗
PubMed1984

Combined intracoronary streptokinase and percutaneous coronary angioplasty for reperfusion of chronic total coronary occlusion.

In a 40 year old man with a 1 month total occlusion of a dominant right coronary artery, persistent angina despite medical management indicated inadequate coronary collateral supply to the posterolateral myocardium originally supplied by the totally occluded vessel. Initial attempts at reperfusion of the chronically occluded vessel with an angioplasty guide wire and balloon were unsuccessful. However, administration of intracoronary streptokinase resulted in partial reperfusion, after which successful wire-guided balloon angioplasty was accomplished. This case illustrates the potential utility of combining a thrombolytic agent with angioplasty in attempting reperfusion for management of selected cases of chronic total coronary artery occlusion.

Adult↗
PubMed1984

Selective impairment of baroreflex-mediated vasoconstrictor responses in patients with ventricular dysfunction.

Cardiac dysfunction in animals has been associated with impairment of arterial and cardiopulmonary baroreflex control of the circulation. Chronic heart failure in human beings is associated with neurohumoral excitation, which could result in part from impairment in the inhibitory influence of baroreflexes. We postulated that (1) patients with left ventricular dysfunction (LVD) have impaired baroreflex modulation of vascular resistance and (2) administration of a digitalis glycoside would immediately restore baroreflex sensitivity. Eleven patients with LVD (NYHA class, 2.8 +/- 0.2, mean +/- SEM; baseline left ventricular ejection fraction, 18 +/- 2%; cardiac index, 2.4 +/- 0.21/min/m2; and pulmonary capillary wedge pressure, 26.0 +/- 3.2 mm Hg) were compared with 17 normal control subjects. We measured forearm vasoconstrictor responses to simulated orthostatic stress with use of lower body negative pressure (LBNP) at -10 and -40 mm Hg to unload cardiopulmonary and arterial baroreceptors. Baseline forearm vascular resistance (FVR) was higher in patients with LVD than in normal subjects: FVRLVD, 68.8 +/- 15.3 U; FVRN, 23.2 +/- 2.1 U (p less than .001). During unloading of baroreceptors with LBNP -10 mm Hg, normal subjects developed vasoconstriction (delta VRN at LBNP -10 mm Hg, +5.7 +/- 1.6 U) but patients with LVD failed to have vasoconstriction and tended to develop vasodilation (delta FVRLVD at LBNP -10 mm Hg, -8.6 +/- 8.5 U) (p = .05, normals vs patients with LVD at LBNP -10 mm Hg). A more marked disparity in response was seen during unloading of baroreceptors of LBNP -40 mm Hg: delta FVRN at LBNP -40 mm Hg, +16.6 +/- 1.5 U; delta FVRLVD at LBNP -40 mm Hg, -10.3 +/- 9.6 U (p less than .001, normals vs patients with LVD). Despite high baseline values for FVR, patients with LVD developed vasoconstriction during intra-arterial infusions of norepinephrine, thereby excluding a nonspecific depression of vascular reactivity as the mechanism for abnormal responses to LBNP in patients with LVD. We also studied the short-term effects of administration of a digitalis glycoside, ouabain 0.0075 mg/kg (seven patients) or lanatoside C (Cedilanid-D) 0.02 mg/kg (three patients), on baroreflex-mediated vasoconstrictor responses to LBNP in the patients with LVD. Digitalis glycoside reduced baseline FVR from 71.8 +/- 16.6 to 48.6 +/- 12.0 U (p less than .02). Responses to LBNP tended to be normalized after administration of digitalis glycoside: delta FVR during LBNP -40 mm Hg, -11.1 +/- 10.5 U before and +7.8 +/- 5.6 U after the drug (p less than .05).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1984

Rethrombosis after reperfusion with streptokinase: importance of geometry of residual lesions.

We tested the hypothesis that lesion rethrombosis after streptokinase reperfusion is related to luminal size of the residual stenosis. Two independent techniques of analyzing coronary angiograms, quantitative coronary angiography and computer-based videodensitometry, were used to estimate the size of the residual lumen immediately after discontinuation of streptokinase. These techniques were selected because they provide independent estimates of cross-sectional area of a lesion with high degrees of reproducibility and minimal observer variability. Twenty-four patients who had undergone successful reperfusion with streptokinase were studied. Seven patients had lesion rethrombosis documented either on a repeat angiogram, at autopsy, or, in one case, by the fact that the patient had an acute transmural infarction resulting in death. Vessel patency was documented by repeat coronary angiography 8 to 14 days after initial streptokinase reperfusion in the other 17 patients. As assessed by quantitative coronary angiography, seven of 13 patients (54%) with minimal luminal cross-sectional areas of less than 0.4 mm2 had rethrombosis. None of the 11 patients with lumens greater than 0.4 mm2 had rethrombosis. In the 17 patients with vessels that remained patent the size of the residual lesion at repeat catheterization was compared with its size immediately after reperfusion with streptokinase. Over the intervening 8 to 14 day interval, an average percentage increase in minimal cross-sectional area of 116 +/- 34% was observed. In seven patients minimal luminal cross-sectional area more than doubled. Integrated optical density, an index of the severity of coronary stenosis derived from computer-based videodensitometry, was also useful in identifying a subgroup of patients at high risk for rethrombosis of lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Computers↗
PubMed1983

Effects of propranolol on reflex vascular responses to orthostatic stress in humans. Role of ventricular baroreceptors.

To evaluate the role of ventricular baroreceptors in humans, we studied the effects of propranolol on reflex vasoconstrictor responses to simulated orthostatic stress. We measured forearm vascular resistance in 10 normal males in the control state and during lower body negative pressure (LBNP) at -10 and -40 mm Hg before and after propranolol (0.1 mg/kg i.v.). Baseline forearm vascular resistance showed no significant change: 23.9 +/- 3.4 U (+/- SEM) before vs 28.0 +/- 0.5 U after propranolol. Reflex increases in forearm vascular resistance during LBNP at -10 and -40 mm Hg were 5.2 +/- 1.2 and 21.2 +/- 6.6 U before and 3.4 +/- 1.2 and 10.6 +/- 2.2 U, respectively, after propranolol. Thus, propranolol significantly (p less than 0.05) reduced responses to LBNP at -40 mm Hg. In contrast to the effects with LBNP, propranolol did not attenuate increases in forearm vascular resistance during the cold pressor test and handgrip, thus excluding a nonspecific depression of reflexes. We also studied the effects of propranolol on carotid baroreflex-mediated vasoconstrictor responses to neck pressure at 15 and 30 mm Hg. Propranolol had no significant effect on the vasoconstrictor responses to neck pressure. In conclusion, propranolol selectively attenuates vasoconstrictor responses to LBNP. We suggest that this results from a propranolol-induced decrease in the activity of cardiac ventricular baroreceptors. The results support the view that ventricular baroreceptors play an important role in reflex adjustments to orthostatic stress in humans.

Adult↗
PubMedDate not supplied

Immediate balloon inflation during ventricular fibrillation complicating coronary angioplasty--an alternative technique to angioplasty system withdrawal: case reports and review.

Two patients are presented in whom ventricular fibrillation occurred during otherwise uncomplicated percutaneous transluminal coronary angioplasty. Rather than withdrawing the angioplasty dilatation system in place in the coronary vessel before instituting resuscitation procedures, immediate balloon inflation was performed while a defibrillator was charged. During balloon inflation, both patients were countershocked, and they recovered stable cardiac rhythm. Postresuscitation hemodynamic and angiographic analysis revealed successful angioplasty results. This report describes an alternative technique to immediate removal of the balloon dilatation system for cardiac arrest complicating coronary angioplasty. Theoretical advantages and potential disadvantages of this technique are discussed.

Aged↗
PubMedDate not supplied

Clinical outcome of emergency repeat coronary artery bypass surgery.

To determine the clinical outcome of patients requiring emergency repeat coronary artery bypass graft (CABG) procedures, we reviewed 23 such procedures performed for ongoing myocardial ischemia refractory to medical management. The operative mortality was 17%. On follow-up, an average of 24.9 months after emergency reoperation, 14 of the 19 survivors (74%) had recurrent angina. As compared to a randomly selected group of 25 patients who underwent elective repeat CABG procedures during the same time period, the incidence of late cardiac events was significantly higher (79% in the emergency group, 30% in the elective surgery group) and fewer patients had received internal mammary artery (IMA) grafts (9% vs 52%). Emergency repeat CABG operations have considerable operative mortality and poor postoperative functional results with the majority of survivors developing recurrent ischemic syndromes within a short period of time.

Aged↗
PubMedDate not supplied

Clinical pitfalls in the non-invasive thrombolytic approach to presumed acute myocardial infarction.

A 32 year old patient who presented with a clinical and electrocardiographic picture consistent with an acute inferior myocardial infarction was treated with intravenous streptokinase without the aid of acute angiographic study. Subsequent evaluation revealed the initial diagnosis of acute infarction to be incorrect and the patient was found to have acute viral myopericarditis. No adverse sequelae resulted from the administration of the thrombolytic agent. The potential and reported adverse effects of a non-invasive thrombolytic approach to presumed acute infarction are reviewed and considerations related to clinical decision making in this setting are discussed.

Adult↗