Prospective randomized comparison of external dacryocystorhinostomy and endonasal laser dacryocystorhinostomy

OBJECTIVE AND DESIGN

The introduction of endonasal laser dacryocystorhinostomy (ENL-DCR) in the early 1990s showed great promise of changing dacryocystorhinostomy into an elegant, minimally invasive procedure from the traditional external dacryocystorhinostomy (EXT-DCR). This prospective, randomized study compares these two operations, their success rates, surgical durations, and postoperative symptoms.

PARTICIPANTS

A total of 64 cases in 61 patients with primary acquired nasolacrimal sac or duct obstruction were divided into 2 subgroups by symptoms (simple epiphora and chronic dacryocystitis). These patients were randomized within both subgroups into 2 operation groups with 32 cases in each group.

INTERVENTION

Altogether, 32 EXT-DCRs and 32 ENL-DCRs were performed. The silicone tube was removed at 6 months after surgery. The final follow-up visit was at 1 year after surgery. The patency of the lacrimal passage was investigated by irrigation, and patients were questioned about their symptoms.

MAIN OUTCOME MEASURES

The patency of the lacrimal passage to irrigation and the duration of surgery were measured.

RESULTS

The success rate at 1 year after surgery was 91% for EXT-DCR and 63% for ENL-DCR after primary surgery. The difference was statistically significant (P = 0.016). The surgical duration for ENL-DCR was three times shorter than for EXT-DCR, the average duration being 23 minutes and 78 minutes, respectively (P < 0.0001).

CONCLUSIONS

The EXT-DCR, when compared with ENL-DCR, seems to provide superior operation results in primary acquired nasolacrimal duct obstruction.

Systemic and regional pCO2 gradients as markers of intestinal ischaemia

OBJECTIVE

We evaluated the response of mixed venous-arterial carbon dioxide (pCO2) to severe intestinal ischaemia produced by gradual occlusion of the superior mesenteric artery (SMA).

DESIGN

Prospective, controlled, experimental study.

SETTING

Animal research laboratory.

SUBJECTS

Twelve domestic pigs.

INTERVENTIONS

SMA blood flow was reduced by 40%, 70% and 100% from the baseline at 60-min intervals.

MEASUREMENTS AND MAIN RESULTS

Haemodynamics were monitored continuously and blood gas values were determined at 30-min intervals. During the SMA occlusion we observed the development of intramucosal acidosis, increased splanchnic oxygen extraction and an increased portal venous-arterial lactate gradient indicative of splanchnic hypoperfusion and intestinal ischaemia. Intramucosal-arterial (p < 0.001), intramucosal-portal venous (p < 0.01) and portal venousarterial (p < 0.01) pCO2 gradients increased during the SMA occlusion, whereas the mixed venous-arterial pCO2 gradient remained unchanged. The mixed venous-arterial pCO2 gradient did not correlate with the intramucosal-arterial pCO2 gradient (r = 0.13), portal venous-arterial lactate gradient (r = 0.10) or splanchnic oxygen extraction (r = 0.14). The portal venous-arterial pCO2 gradient correlated with the portal venous-arterial lactate gradient (r = 0.75, p < 0.001) and splanchnic oxygen extraction (r = 0.79, p < 0.001), but not with the intramucosal-arterial pCO2 gradient (r = 0.35).

CONCLUSION

Despite clear evidence of severe splanchnic hypoperfusion, as shown by regional hypercarbia and lactate production, the mixed venous-arterial pCO2 gradient did not reflect splanchnic hypoperfusion.

Significance of coronary artery bypass grafting-associated conduction defects

The incidence of permanent atrioventricular conduction defects (CDs) caused by coronary artery bypass grafting (CABG) varies from 5% to 43% if cold crystalloid or blood cardioplegia is used for myocardial preservation. However, the long-term effects of CDs on clinical outcome are not well known. In this study we compared the outcome of 52 patients with permanent CABG-associated CDs (CD+) to 47 patients without CDs (CD-) after a 3-year follow-up. Recovery of CDs was found in 2 patients during the follow-up. There were no significant differences between groups in late mortality, cardiac or neurologic events, or capability to work. Although exercise capacity was similar, the exercise-limiting symptom more often was chest pain or dyspnea in the CD+ group than in the CD- group (p = 0.001). Left ventricular ejection fractions at rest and at 50-W workload level were lower in the CD+ group (p = 0.03 to 0.05). In addition, CD+ patients with left bundle branch block or cardiac pacemaker had significantly lower ejection fraction at maximal workload level than patients without CDs (p = 0.03). No significant differences were observed between the groups in the potential risk for ventricular arrhythmias according to signal-averaged electrocardiograms. In conclusion, the clinical outcome of patients with CDs after CABG operations is almost comparable to those without CDs during a 3-year follow-up. However, patients with CDs have lower left ventricular systolic function and more often have chest pain or dyspnea as the exercise-limiting symptom than patients without CDs.

Age and gender dependency of baroreflex sensitivity in healthy subjects

We evaluated the correlates of baroreflex sensitivity (BRS) in healthy subjects. The study consisted of 117 healthy, normal-weight, nonsmoking male and female subjects aged 23-77 yr. Baroreflex control of heart rate was measured by using the phenylephrine bolus-injection technique. Frequency- and time-domain analysis of heart rate variability and an exercise test were performed. Plasma norepinephrine, epinephrine, insulin, and arginine vasopressin concentrations and plasma renin activity were measured. In the univariate analysis, BRS correlated with age (r = -0.65, P < 0.001), diastolic blood pressure (r = -0.47, P < 0.001), exercise capacity (r = 0.60, P < 0.001), and the high-frequency component of heart rate variability (r = 0.64, P < 0.001). There was also a significant correlation between BRS and plasma norepinephrine concentration (r = -0.22, P < 0.05) and plasma renin activity (r = 0.32, P < 0.001). According to the multivariate analysis, age and gender were the most important physiological correlates of BRS. They accounted for 52% of interindividual BRS variation. In addition, diastolic blood pressure and high-frequency component of heart rate variability were significant independent correlates of BRS. BRS was significantly higher in men than in women (15.0 +/- 1.2 vs. 10.2 +/- 1.1 ms/mmHg, respectively; P < 0.01). Twenty-four percent of women > 40 yr old and 18% of men > 60 yr old had markedly depressed BRS (< 3 ms/mmHg). We conclude that physiological factors, particularly age and gender, have significant impact on BRS in healthy subjects. In addition, we demonstrate that BRS values that have been proposed to be useful in identifying postinfarction patients at high risk of sudden death are frequently found in healthy subjects.

Group II phospholipase A2 in nasal fluid, mucosa and paranasal sinuses

The aim of this study was to determine the type of phospholipase A2 (PLA2) in nasal fluid and to demonstrate its cellular origin. The concentration of group II PLA2 was high (591.5 micrograms/l) in nasal fluid compared with serum level (10.8 micrograms/l) and the fluid of paranasal sinuses (10.6 micrograms/l). Methacholine stimulated nasal fluid contained only small amounts (19.1 micrograms/l) of group II PLA2 when the flow of tear fluid through the nasolacrimal duct was obstructed. Occasional glands secreting group II PLA2 were found in nasal and paranasal mucosa by immunohistochemistry. Lysozyme was found in the majority of mucosal glands. It was concluded that nasal and paranasal mucosal glands contain group II PLA2. In nasal fluid, however, PLA2 is mainly derived from tear fluid.

Exercise-induced T-wave alternans as a marker of high risk in patients with hypertrophic cardiomyopathy

Microvolt-level T-wave alternans (alternating morphology from beat to beat) during atrial pacing and exercise may predict ventricular tachycardia (VT) and fibrillation (VF) in ischemic heart disease. We tested whether such alternans during exercise could identify high-risk patients with hypertrophic cardiomyopathy (HCM). We studied 14 HCM patients and 9 normal control subjects for T-wave alternans u sing the CH2000 system with 7 multisegment electrodes in a Frank orthogonal (XYZ) configuration. Bicycle ergometer exercise was used to increase the heart rate (HR) to 95-110 beats/min. Seven patients were at high risk for ventricular arrhythmias (1 with sustained VT, 3 with abnormal paced ventricular electrograms as seen in VF survivors, and 3 with nonsustained VT and/or an adverse family history), and the other 7 were at low risk. T-wave alternans was present if alternans > 1.9 microV was consistently present with the HR in excess of a patient-specific HR threshold. Alternans was found in 5 of 7 high-risk patients (71%) vs none of 7 low-risk patients or 9 control subjects (p < 0.025 and p < 0.01, respectively). Notably, all 4 patients with sustained VT or abnormal ventricular electrograms showed alternans. Thus, high-risk patients with HCM often show T-wave alternans. Microvolt-level alternans during exercise may be a useful marker for ventricular arrhythmic risk in patients with HCM.

Cardiac sympathetic denervation in patients with coronary artery disease without previous myocardial infarction

Myocardial infarction damages sympathetic nerve fibers coursing through the infarct zone. In this study we investigated whether coronary artery disease without myocardial infarction results in sympathetic denervation. We examined 12 patients without a history of previous myocardial infarction and 19 postinfarction patients. 1-123 metaiodobenzylguanidine (MIBG) and technetium-99m sestamibi (MIBI) single-photon emission tomography were conducted at rest to determine the extent of denervated myocardium and the extent of myocardium with reduced perfusion, respectively. In addition, myocardial perfusion during exercise was assessed with MIBI. A MIBG or MIBI defect was determined as being regional uptake of < or =30% of the maximal myocardial activity. All but 1 patient without previous infarction had MIBG defects. MIBG defects (10.3 +/- 8.5% of left ventricular mass) were significantly larger than MIBI defects at rest (2.4 +/- 3.2%, p <0.001) and during exercise (4.8 +/- 6.1%, p <0.05). In multiregression analysis, the size of an MIBG defect was associated with severity of coronary stenoses (> or =90% of lumen diameter; p <0.05), but not with age, number of significant stenoses (> or =50% of lumen diameter), left main disease, functional class, left ventricular ejection fraction, angina pectoris, maximal ST depression, or mean workload during exercise test. MIBG and MIBI defects were significantly larger in patients with severe coronary stenoses than in patients with moderate stenoses (50% to 89% of lumen diameter) (16.4 +/- 8.9% vs 6.0 +/- 5.2% [p <0.05] and 5.0 +/- 3.1% vs 0.6 +/- 1.3% [p <0.001], respectively). The size of MIBG (16.1 +/- 8.9%) and MIBI defects (7.3 +/- 6.5%) at rest in postinfarction patients did not differ from patients with severe stenoses. Our study demonstrates that cardiac adrenergic tissue is very sensitive to ischemia and that regional cardiac sympathetic denervation can occur in patients with stable coronary artery disease without previous myocardial infarction.

Systemic and regional effects of experimental gradual splanchnic ischemia

PURPOSE

We evaluated the effects of gradual intestinal ischemia on systemic and regional haemodynamics and oxygen transport.

MATERIALS AND METHODS

Superior mesenteric artery (SMA) blood flow was decreased by 40%, 70%, and 100% for 60-minute periods and thereafter released in 12 pigs. Hemodynamic changes were monitored continuously, and the intestinal perfusion was evaluated by changes in portal vein-arterial lactate gradient, intramucosal pH, tonometric Pco2, tonometric-portal vein Pco2 gradient, and regional oxygen extraction.

RESULTS

Local signs of intestinal hypoperfusion developed during the SMA occlusion. Intramucosal pH and portal vein pH decreased from 7.18 +/- 0.04 to 6.81 +/- 0.04 (P < .01) and from 7.36 +/- 0.01 to 7.25 +/- 0.03 (P < .05), respectively. Intramucosal Pco2 and tonometric-portal vein Pco2 gradient increased from 12.4 +/- 1.3 to 21.2 +/- 1.8 kPa (P < .01) and from 6.0 +/ 1.3 to 14.0 +/- 1.9 kPa (P < .05), respectively. Portal vein-arterial lactate gradient and splanchnic oxygen extraction increased from 0.02 +/- 0.07 to 2.32 +/- 0.47 mmol/L (P < .01) and from 0.44 +/- 0.03 to 0.60 +/- 0.03 (P < .05), respectively. Systemic changes observed during the SMA occlusion were reduction of cardiac index (161 +/- 12 to 114 +/- 8 mL/min/kg, P < .01) and pulmonary capillary wedge pressure (4 +/- 1 to 3 +/- 1 mm Hg) and increase in heart rate (124 +/- 5 to 173 +/- 11 beats/ min, P < .01) and mean arterial pressure (79 +/- 3 to 104 +/- 5 mm Hg, P > .01). Systemic oxygen extraction increased (P > .05), arterial pH increased (P < .05), and arterial lactate decreased (P < .01) during the SMA occlusion. Splanchnic ischemia defined as an increase in portal vein-arterial lactate gradient above mean +2 SD of the baseline occurred at 93 +/- 15 minutes corresponding 70% SMA occlusion.

CONCLUSION

We conclude that signs of tissue hypoperfusion started to develop at 70% SMA occlusion and that regional tissue hypoperfusion in the splanchnic region may develop without any systemic signs of oxygen supply/demand mismatch.

Measurement of protein concentration of aqueous humour in vivo: correlation between laser flare measurements and chemical protein determination

We studied the correlation between laser flare cell meter photon count/ms and actual protein concentration both in vitro and in vivo. Laser flare cell meter measurement of human albumin concentrations of 0 to 10 g/l showed photon counts/ms from 0.3 +/- 0.3 to 78.9 +/- 3.9. There was a statistically highly significant linear correlation between photon count/ms and human albumin concentration (r = 0.98, p = 0.0001). Laser flare cell meter measurements were done on 39 cataract patients with the mean age of 77.9 +/- 6.7 years. Aqueous humour obtained by peroperative paracentesis was analysed for total protein. The mean photon count/ms before pupillary dilatation was 11.93 +/- 6.03. There was a significant linear correlation (r = 0.4, p = 0.019) between the photon count/ms after pupillary dilatation (mean 14.73 +/- 12.9, range 2.6-62.4) and anterior chamber protein concentration (mean 0.62 +/- 0.27, range 0.23-1.3 g/l) with the linear regression formula being y = 0.231 x -1.105 where y = log protein concentration (g/l) and x = log of photon count/ms. Laser flare cell meter photon counts/ms may be converted into an equivalent anterior chamber total protein concentration using this formula.

Quantitative determination of aqueous flare and cells in healthy eyes

We studied 263 eyes of 141 normal subjects, 33 men and 108 women, including 129 Finns and 12 Ibero-Americans, with the age ranging between 12 and 89 (mean 43.0 +/- 20.4) years using the Kowa FC-1000 laser flare cell meter. The mean photon count/ms was 4.5, it was 3.1 in the age groups of 10-19 years and 11.5 in the age group of 80 years or over; the increase with age was statistically significant (p = 0.0001). There were no significant differences in the photon count/ms between right and left eyes (p = 0.75), between sexes (p = 0.61), or between Ibero-Americans and age-matched Finns (p = 0.62). The mean cell count was 1.1 and there were no significant changes between the right and left eyes (p = 0.56) or between different age (p = 0.38), sex (p = 0.32) and race (p = 0.64) groups. There were no significant differences in the mean photon count/ms (p = 0.97) and cell counts (p = 0.35) between the first and second measurements 5 min later. There was no subject-within variability after 24 h and 7 days in the flare (p = 0.95) and cell counts (p = 0.89).

Bacteriology of lacrimal duct obstruction in adults

AIMS

To determine the current bacteriology of lacrimal duct obstruction (LDO) and to relate the bacteriological findings to the type of symptoms.

METHODS

127 samples were obtained from the lacrimal sac in 118 consecutive adult patients with LDO, including nine bilateral cases.

RESULTS

Altogether, 156 isolates were recovered from the 127 samples cultured. Cultures were positive from 84% of the samples. Gram positive bacteria were isolated in 79 (62%) samples. The most frequently cultured bacterial species was Staphylococcus epidermidis, representing 27% of the isolates. Gram negative bacteria were recovered from 26 (20%) samples, and these bacteria were statistically significantly more common in cases with copious discharge than in cases with minor discharge (p = 0.000). Cases with simple stenosis of the lacrimal duct (SSLD) showed significantly less Streptococcus sp (p = 0.004) and Gram negative organisms (p = 0.004) than those with chronic dacryocystitis.

CONCLUSION

The bacteriology of SSLD resembles that of normal conjunctival flora. Chronic dacryocystitis in adults is associated with an increased proportion of Gram negative bacteria which may be a reservoir for postoperative intraocular infection. They should also be taken into account in selecting antimicrobial prophylaxis in lacrimal drainage surgery.

Is vagal innervation to the atrioventricular node impaired after radiofrequency ablation of the slow atrioventricular nodal pathway?

To assess the potentially adverse effects of RF catheter ablation (RFCA) of the slow AV nodal pathway on the parasympathetic innervation to the AV node in patients with AV nodal reentrant tachycardia (AVNRT), AV nodal conduction was evaluated following vagal stimulation by means of a phenylephrine bolus injection (200 micrograms) before and after RFCA in ten patients (mean age, 37 +/- 14 years). Nine patients with AV reentrant tachycardia (AVRT) due to a left free wall accessory pathway served as a control group (mean age of 37 +/- 12 years). Whereas no prolongation of the AH interval was observed in the AVNRT group following the phenylephrine bolus during sinus rhythm, despite a significant slowing in sinus rate, phenylephrine administration in AVRT patients was associated with both slowing of the sinus rate and prolongation of the AH interval. Following successful RFCA, the same responses were observed. To delineate the indirect effect of heart rate on AV conduction in response to the phenylephrine bolus, the AH interval was also measured during fixed atrial pacing. A marked prolongation of the AH interval occurred in both groups following phenylephrine administration. This prolongation was biphasic in 50% of AVNRT patients before ablation, suggesting a predominant effect of vagal stimulation on the fast AV nodal pathway. RFCA was associated with disappearance of discontinuous AV conduction in all but one patient with AVNRT. Vagal stimulation caused the same amount of AH interval prolongation as before RFCA in both study groups. In conclusion, patients with AVNRT have a preserved modulation of AV nodal conduction in response to vagal stimulation during sinus rhythm. In addition, vagal stimulation seems to exert a predominant effect on the fast AV nodal pathway. RFCA of the slow AV nodal pathway in patients with AVNRT does not cause detectable damage to the vagal innervation to the AV node.

Lacrimal bone thickness at the lacrimal sac fossa

BACKGROUND AND OBJECTIVE

Because laser dacryocystorhinostomy techniques have become more popular during the past few years, interest has grown concerning the anatomic structures that need to be penetrated in these procedures. The authors therefore studied the thickness and the histologic type of the lacrimal bone at the lacrimal sac fossa.

PATIENTS AND METHODS

The thickness of 69 lacrimal bones at the lacrimal sac fossa from 48 patients was measured.

RESULTS

The mean thickness was 106 microns. In 67% of the patients the mean thickness of individual lacrimal bone was less than 100 microns and in 4% it was more than 300 microns. The thinnest measured cross section of the lacrimal bone sample was 11 microns and the thickest was 722 microns. The lacrimal bone was composed of a thin plate of lamellar bone.

CONCLUSION

In most cases the lacrimal bone at the lacrimal sac fossa is so thin that it can be easily penetrated with most surgical instruments.

Sympathetic reinnervation after acute myocardial infarction

Myocardial infarction produces sympathetic denervation of the necrotic myocardium and noninfarcted myocardium apical to the injury. Proof of sympathetic reinnervation after myocardial infarction has, however, remained elusive. In this study, we investigated whether cardiac sympathetic reinnervation occurs in men recovering from myocardial infarction. I-123 metaiodobenzylguanidine (MIBG), I-123 paraphenylpentadecanoic acid, and Tc-99m sestamibi scintigraphic imaging were conducted in 13 men 3 and 12 months after a first myocardial infarction to determine the extent of denervated myocardium, the size of the infarct, and the size of the myocardium with reduced perfusion, respectively. A defect was determined as regional uptake of < or = 30% of the maximal myocardial activity. The size of the MIBG defect was not significantly different between 3 and 12 months after infarction (17 +/- 8% and 18 +/- 8% of left ventricular mass, respectively). There was also no significant change in the extent of viable but denervated myocardium at 3 and 12 months (average 9 +/- 6% and 10 +/- 5%, respectively). MIBG activity of the infarct zone (expressed as a percentage of MIBG activity of the myocardium with normal perfusion) did not change (17 +/- 13% and 20 +/- 16%), whereas MIBG activity of the periinfarct zone increased during follow-up (32 +/- 11% and 41 +/- 14%, p < 0.01). This was associated with an increase in periinfarct I-123 paraphenylpentadecanoic acid activity (40 +/- 11% and 48 +/- 9%, p < 0.05), but not Tc-99m sestamibi activity (48 +/- 10% and 48 +/- 11%). In conclusion, we did not observe sympathetic reinnervation in the infarct zone between 3 and 12 months after myocardial infarction. However, MIBG activity of the periinfarct zone increased, suggesting partial reinnervation, and this was associated with a recovery of myocardial metabolic activity of the periinfarct zone.

Prediction of atrioventricular block during radiofrequency ablation of the slow pathway of the atrioventricular node

BACKGROUND

Selective radiofrequency (RF) ablation of the slow pathway is an effective treatment for atrioventricular (AV) nodal reentry tachycardia. A previous report showed that rapid junctional tachycardia (JT) caused by RF associated with loss of ventriculoatrial (VA) conduction is related to increased risk for AV block. However, this can be difficult to detect during energy delivery, and more importantly, it cannot be measured before the onset of RF energy delivery. The aim of our study was to determine whether measurements made from electrograms could be used to predict the risk of AV block before RF energy is delivered.

METHODS AND RESULTS

Fifty-eight patients underwent 63 selective slow pathway RF ablation procedures. In 46 (26.9%) of 172 JTs caused by RF, VA block was observed, and in 11 this was followed by AV block of various degrees. Electrograms before each application of RF were analyzed for the interval between the atrial signals in the His bundle catheter and in the distal mapping catheter [A(H)-A(Md)], the interval between the atrial signals in the His bundle catheter and in the proximal coronary sinus catheter [A(H)-A(CS)], the AV ratio, and the presence of a slow pathway potential or a fractionated atrial signal in the distal mapping catheter. Mean cycle length (CL) of JT was calculated if it consisted of at least 10 beats. These parameters were compared between patients with JT who developed VA block and subsequent AV block (group 1), patients with JT and VA block but without subsequent AV block (group 2), and patients with JT without VA block (group 3). The A(H)-A(Md) interval was significantly shorter in group 1 (17 +/- 8 ms) than in groups 2 (33 +/- 8 ms, P < .001) and 3 (32 +/- 10 ms, P < .001), whereas the A(H)-A(Md) intervals of groups 2 and 3 did not differ from each other. CL of JT, A(H)-A(CS) interval, AV ratio, presence of a slow pathway potential, or a fractionated atrial electrogram were not related to the occurrence of AV block.

CONCLUSIONS

The A(H)-A(Md) interval provides an electrophysiological marker that can be used in addition to the radiological catheter position to assess the risk for AV block before onset of RF delivery. CL of JT and occurrence of VA block are not related to the risk of AV block.

Effect of posture on baroreflex sensitivity in healthy subjects

In this study we investigated whether body position has significant effects on baroreflex sensitivity in healthy subjects. Baroreflex sensitivity was calculated from pressure overshoot after the release of a Valsalva strain in the supine and sitting positions in 10 subjects. At rest, no difference was found in supine and sitting mean R-R intervals (837 +/- 82 and 858 +/- 86 ms, respectively), whereas systolic and diastolic blood pressures were lower in the supine position (111.3 +/- 24.6 vs. 141.2 +/- 12.6 mmHg, P < 0.01 and 54.8 +/- 14.7 vs. 75.6 +/- 13.4 mmHg, P < 0.001, respectively). Baroreflex sensitivity in the supine (9.0 +/- 4.1 ms x mmHg-1) and sitting positions (8.8 +/- 4.9 ms x mmHg-1) did not differ significantly from each other. The correlation between supine and sitting baroreflex sensitivity was 0.96 (P < 0.001) and in 9 out of 10 subjects the discrepancy between supine and sitting baroreflex sensitivity was < 2.0 ms x mmHg-1. We conclude that baroreflex sensitivity measured in the supine and sitting positions do not differ significantly from each other.

Good exercise capacity at hospital discharge predicts recovery of baroreflex sensitivity after myocardial infarction

Myocardial infarction results in depressed baroreflex sensitivity, which has been shown to be associated with increased risk of ventricular arrhythmias and sudden death. We measured baroreflex sensitivity in 37 patients with acute myocardial infarction before hospital discharge and 3 months after the infarction to find out whether the baroreflex sensitivity recovers during that period. In addition, baroreflex sensitivity was assessed in 15 healthy controls. Baroreflex sensitivity was assessed from the regression line relating the change in R-R interval to the change in systolic blood pressure following an intravenous bolus injection of phenylephrine. There was a wide inter-individual variation in the change of baroreflex sensitivity (delta baroreflex sensitivity) in infarction patients, but the average baroreflex sensitivity showed no significant change during the 3-month follow-up (10.2 + 5.6 to 11.8 +/- 7.5 ms.mmHg-1, ns) and remained lower than the baroreflex sensitivity of the controls (16.4 +/- 9.7 ms.mmHg-1, P < 0.05). delta Baroreflex sensitivity correlated significantly with exercise capacity measured before hospital discharge. When the patients were divided into tertiles according to the delta baroreflex sensitivity (-3.3 +/- 1.5 ms.mmHg-1 in the lowest tertile, 1.0 +/- 1.0 ms.mmHg-1 in the middle tertile and 7.5 +/- 4.0 ms.mmHg-1 in the highest tertile) the exercise capacity was found to increase from the lowest to the highest tertile (exercise time 357 +/- 115 s, 418 +/- 126 s and 461 +/- 141 s, respectively; P < 0.05 lowest vs highest tertile). Patients with a low exercise tolerance (exercise time < 360 s) showed a significantly smaller delta baroreflex sensitivity than patients with a good exercise tolerance (exercise time > or = 480 s) (-0.5 +/- 4.4 vs 5.3 +/- 5.4 ms.mmHg-1, P < 0.05), respectively. delta Baroreflex sensitivity was not related to the location or type of infarction, thrombolytic therapy, presence of angina pectoris or left ventricular function at the time of discharge. In conclusion, exercise capacity assessed before hospital discharge seems to be a predictor of baroreflex sensitivity recovery in patients with a recent myocardial infarction.

Baroreflex sensitivity and neurohormonal activation in patients with acute myocardial infarction

OBJECTIVE

To examine the relationship between baroreflex sensitivity and neurohormonal activation in patients with an acute myocardial infarction.

METHODS

Baroreflex sensitivity, plasma noradrenaline, atrial natriuretic factor, endothelin-1, and plasma renin activity were measured in 37 male patients about 10 days after their first myocardial infarction, and in 15 healthy controls. Baroreflex sensitivity was assessed from the regression line relating the change in RR interval to the change in systolic blood pressure following an intravenous bolus injection of phenylephrine. The measurements were repeated after a follow up of three months.

RESULTS

There was a significant inverse correlation between baroreflex sensitivity and plasma noradrenaline measured before hospital discharge (r = -0.43, P < 0.01). Patients with increased plasma noradrenaline (> or = 2SD above the mean of the age matched control group) had significantly lower baroreflex sensitivity than patients with normal plasma noradrenaline (8.7 (SD 4.6) v 12.1 (6.1) ms/mm Hg, P < 0.05). The change in baroreflex sensitivity during the follow up showed a significant inverse correlation with the change of plasma noradrenaline (r = -0.450, P < 0.01). Furthermore, when patients with increased plasma noradrenaline before hospital discharge were analysed separately, baroreflex sensitivity at three months in patients in whom plasma noradrenaline had decreased to normal values was significantly higher than in patients in whom plasma noradrenaline had remained increased (14.6 (5.7) v 8.1 (8.1) ms/mm Hg, P < 0.05). On the other hand, baroreflex sensitivity was not related to the levels of plasma atrial natriuretic factor, plasma endothelin-1, or plasma renin activity. Neither was any relationship found between change in baroreflex sensitivity and change in plasma atrial natriuretic factor, endothelin-1, or plasma renin activity during the follow up.

CONCLUSIONS

The impairment baroreflex sensitivity after myocardial infarction was associated with increased concentration of plasma noradrenaline, that is, sympathetic activation, but not with plasma atrial natriuretic factor, endothelin-1, or plasma renin activity. Baroreflex sensitivity provides information about cardiac vagal control as well as about the balance of cardiac sympathetic-parasympathetic regulation.

Myocardial sympathetic nervous dysfunction detected with iodine-123-MIBG is associated with low heart rate variability after myocardial infarction

The association between myocardial sympathetic innervation and heart rate variability after myocardial infarction was studied in a group of 12 men (aged 30-65 yr) 3 mo after their first myocardial infarction.

METHODS

Viable myocardium was imaged using 123I-phenylpentadecanoic acid (pPPA). Functioning myocardial sympathetic nervous tissue was imaged using [123I]-metaiodobenzylguanidine (MIBG). Heart rate variability was measured as the ratio of maximum-to-minimum RR intervals in ECG during deep breathing.

RESULTS

The patients were divided into normal (n = 6) and low (n = 6) heart rate variability groups. Myocardial infarction size (pPPA defect) was comparable in the normal and low heart rate variability groups. Even the MIBG defect size was not significantly different in the normal and low groups, the portion of viable myocardium with impaired sympathetic innervation (MIBG defect minus pPPA defect) was significantly greater in the low heart rate variability group than in the normal group.

CONCLUSION

The extent of viable myocardium with disturbed sympathetic innervation was greater in patients with low heart rate variability as compared to those with normal heart rate variability 3 mo after myocardial infarction.

Metabolic stress modifies the thermogenic effect of dobutamine in man

OBJECTIVE

To study if metabolic stress modifies the thermogenic effect of dobutamine.

DESIGN

Prospective, increasing dose, pharmacologic study.

SETTING

Laboratory of the Department of Intensive Care Unit at a university hospital.

SUBJECTS

Twelve normal volunteers.

INTERVENTIONS

Dobutamine hydrochloride was infused to 12 healthy male volunteers starting at a dose of 2 micrograms/min/kg and gradually increased to 4 and 6 micrograms/min/kg. Each dose of dobutamine was infused for 20 mins. Metabolic stress was induced in six of the 12 volunteers using a triple hormone infusion (epinephrine, cortisol, and glucagon) before dobutamine, and was continued at a constant rate during the dobutamine infusion. The remaining six volunteers served as the control group and received only dobutamine.

MEASUREMENTS AND MAIN RESULTS

Oxygen consumption (VO2) was measured using a metabolic monitor. Arterial blood pressure was measured noninvasively, and cardiac output was monitored by Doppler echocardiography. Plasma concentrations of dopamine, norepinephrine, and epinephrine were measured in both groups. In the triple hormone group, blood was sampled to measure concentrations of insulin, glucagon, cortisol, free fatty acids, and glycerol to ensure the presence of a metabolic stress reaction. At the maximum dose, dobutamine induced a 19% increase (from 140 +/- 17 to 166 +/- 17 mL/min/m2) in VO2 in the control group and an 11% increase (from 167 +/- 10 to 184 +/- 13 mL/min/m2) in the triple hormone group (p < .05 between the two groups) compared with baseline. No change in the respiratory exchange ratio was seen. The triple hormone infusion alone induced hypermetabolism, a marked hemodynamic response, and increased lipolysis.

CONCLUSIONS

Stress, induced by a triple hormone infusion, diminishes the thermogenic effect of dobutamine. In the clinical setting, a > 10% to 15% increase in VO2 in response to dobutamine may not be explained just by the thermogenic effect of the drug.

Phospholipase A2 content of aqueous humour in cataract patients

In order to determine the content of group II phospholipase A2 in the aqueous humour we studied 41 cataract patients including 8 men and 33 women with age ranging between 65 and 92 (mean +/- SD being 77.0 +/- 6.7) years. In all patients preoperative biomicroscopy showed neither aqueous flare nor cells. Eleven patients (26.8%) had pseudoexfoliation syndrome. Aqueous humour tap was done at the beginning of cataract surgery before perforating the corneoscleral wound. We used time-resolved fluoroimmunoassay for the detection of group II phospholipase A2 in the aqueous humour. The group II phospholipase A2 content in the aqueous humor varied between less than measurable (in 23 patients) and 3.3 ng/ml, with an interquartile range from less than measurable to 1.4 ng/ml. There was no significant difference in the group II phospholipase A2 content of the aqueous humour whether or not the patient had pseudoexfoliation syndrome. The results show that the aqueous humour of cataract patients contains only minute amounts of group II phospholipase A2.

Day-to-day variability of cardiac autonomic regulation parameters in normal subjects

We examined the reproducibility of day-to-day variability in cardiovascular autonomic nervous function parameters (classical clinical tests and domain analysis of heart rate variability) in four healthy men during a period of 1 working week. The results did not show any significant difference in any of the parameters over the five repeated measurements. The maximum-minimum difference as percentage of the mean was under 15% for expiration to inspiration (E/I) ratio, Valsalva ratio, tachycardia ratio, 30/15 ratio, acceleration index and brake index; about 45% for baroreflex sensitivity for systolic and diastolic blood pressure and for root mean square difference (RMSSD) of successive R-R intervals; about 65-85% for low and high frequency bands, total power and medium to high frequency ratio; and about 125% for medium frequency band. The intraclass correlation coefficient (ICC) values showed that the agreement for classical autonomic parameters (except for brake index) was good. ICC for RMSSD, baroreflex sensitivity for systolic blood pressure and the spectral estimates of heart rate variation were less good. Coefficient of variation (CV) was 4% for E/I ratio, 2% for 30/15 ratio, 6% for Valsalva, 3% for tachycardia ratio, 4% for acceleration index and 5% for brake index. CV for baroreflex sensitivity and for RMSSD was about 20%. It is concluded that the variation in baroreflex sensitivity is clearly larger than in the classical autonomic nervous function parameters. One-minute fixed pace breathing period seems to be too short to allow reproducible measurement of RMSSD and the spectral parameters of heart rate variation. Learning effect could be excluded.