Effects of Class I drugs on atrial fibrillation

This article reviews our knowledge about the efficacy of Class I antiarrhythmic agents, especially quinidine, propafenone, and flecainide, for pharmacologic conversion of atrial fibrillation to sinus rhythm. When given intravenously or orally for the long term, conversion rates between 50% and 90% are reported for restoration of sinus rhythm as well as for maintenance of sinus rhythm after DC cardioversion. Based on transtelephonic monitoring of arrhythmia recurrences as well as tolerance, Class IC agents appear to be especially effective for suppressing clinical symptoms in patients with paroxysmal atrial fibrillation. For patients who develop atrial fibrillation following coronary artery surgery, Class I agents are the second choice of treatment only. The concept of single oral loading with Class IC agents for conversion of atrial fibrillation appears attractive, but more data are needed before we conclude that it is efficacious as well as safe when given to ambulatory patients. Because all Class I antiarrhythmic agents have the potential for lethal proarrhythmia, the greatest and as yet unsettled issue is safety. Until the advent of large-scale and long-term trials demonstrating the efficacy and safety of Class I agents for the treatment of patients with atrial fibrillation, this strategy, although very popular to suppress frequent and unpleasant symptoms due to atrial fibrillation, cannot be regarded as firmly established.

Experience with pectoral versus abdominal implantation of a small defibrillator. A multicenter comparison in 778 patients. European Jewel Investigators

AIMS

The aim of the study was to examine the results of implanting small sized cardioverter defibrillators in the pectoral as opposed to the abdominal area. Hitherto. owing to the large size of the early defibrillators, the site of implantation had been confined to the abdomen.

METHODS

Between 30 March 1993 and 1 November 1994, 778 patients from 63 centres in 14 countries underwent their first device implantation. The study was set up to evaluate the safety and the efficacy of Medtronic models 7219 D, a multi-lead abdominal/pectoral implantable cardioverter defibrillator, and 7219 C, a pectoral single-lead Active Can implantable cardioverter defibrillator. There were 155 abdominal and 623 pectoral implants. Survival data were comparable during a mean follow-up period of 4.0 +/- 4.6 months, with no difference regarding the pectoral placement of single (n = 392) or multi-lead (n = 231) devices. The only significant difference was related to severe lead-related events: 5.3% in the pectoral vs 11.6% the abdominal group (P < 0.05). These events were mainly related to lead dislodgement. Kaplan-Meier estimates showed that both single and multi-lead systems, in either the pectoral or abdominal position, demonstrated a similar severe adverse event-free survival.

CONCLUSION

These findings suggest that an implantable cardioverter defibrillator (18 mm thick, 80 cc volume, 129 g weight) can be implanted in the pectoral position without an increase in clinically relevant adverse events compared to abdominal implantation. Pectoral implantation was associated with significantly reduced lead-related severe adverse event rate.

Fast pathway ablation in patients with common atrioventricular nodal reentrant tachycardia and prolonged PR interval during sinus rhythm

AIMS

This study aimed to clarify the safety and efficacy of selective fast pathway ablation in patients with atrioventricular nodal reentrant tachycardia and a prolonged PR interval during sinus rhythm. Such patients have been reported to have an increased incidence of complete atrioventricular block.

METHODS AND RESULTS

In this study, the earliest retrograde atrial activation during atrioventricular nodal reentrant tachycardia and right ventricular stimulation was localized. Fast pathway ablation was then performed in five patients with the common form of atrioventricular nodal reentrant tachycardia and a prolonged PR interval. Three of the five patients had almost incessant atrioventricular nodal reentrant tachycardia. Radiofrequency catheter ablation induced a complete ventriculo-atrial block during right ventricular stimulation in four patients and a marked prolongation of ventriculo-atrial conduction during right ventricular stimulation in one. Non-inducibility of common atrioventricular nodal reentrant tachycardia with and without isoproterenol was achieved in all five patients. The PR interval increased from 254 +/- 53 ms to 276 +/- 48 ms and the atrio-His interval from 172 +/- 46 ms to 192 +/- 45 ms. Second- or third-degree atrioventricular block did not occur during the ablation procedure. During the followup of 19 +/- 20 months none of the patients developed symptoms suggestive of atrioventricular nodal reentrant tachycardia or evidence of second- or third-degree atrioventricular block.

CONCLUSION

These data suggest that atrioventricular node (retrograde) fast pathway ablation can apparently be safely performed in patients with common atrioventricular nodal reentrant tachycardia and a prolonged PR interval during sinus rhythm.

[Radiofrequency catheter ablation of atrial flutter and atrial fibrillation]

Radiofrequency catheter ablation is now considered as a curative approach in patients with typical atrial flutter. Typical atrial flutter is due to a macrore-entrant circuit within the right atrium and it can be eliminated by a linear lesion in the isthmus between the tricuspid annulus and the vena cava inferior. The electrophysiological criterion of a bidirectional isthmus block has been shown to reduce the recurrence rate of atrial flutter after catheter ablation, thus achieving long-term cure of typical atrial flutter. Acute success rates of 85 to 90% and recurrence rates of 10 to 15% have been reported. The risk of paroxysmal atrial fibrillation continues to be clinically relevant in patients who underwent successful ablation of atrial flutter, in particular in patients with previously documented atrial fibrillation. The incidence of a new onset of atrial fibrillation after ablation of atrial flutter seems to be approximately 20%. Isthmus ablation has also been shown to be beneficial for the majority of patients with typical atrial flutter and atrial fibrillation: In addition to an elimination of typical atrial flutter the isthmus ablation apparently reduces the incidence of paroxysmal atrial fibrillation. At present, atrial fibrillation can only be treated by catheter ablation as a curative approach in the rare cases where an accessory pathway, an AV nodal re-entrant tachycardia, typical atrial flutter or an ectopic atrial tachycardia is the induction mechanism of the atrial fibrillation. The majority of patients with atrial fibrillation is apparently not amenable to a curative local ablation. While AV junction ablation and AV node modification can palliate some of the symptoms of atrial fibrillation by a control of ventricular rate, the arrhythmia persists with the loss of AV synchrony and continued risk of thromboembolism. The surgical MAZE procedure implies a compartimentation of the atria by surgical incisions resulting in areas to small to sustain the arrhythmia. Based on this procedure experimental and clinical studies are currently performed in order to develop catheter ablation cure of atrial fibrillation.

[Analysis of functional changes in ventricular late potentials for risk assessment of ventricular tachycardias after myocardial infarct]

BACKGROUND

Electrophysiological abnormalities during ischaemia and increased heart rate may influence the detection of ventricular late potentials in the surface electrocardiogram. Whether the analysis of functional changes adds information to the risk stratification of patients prone to ventricular tachycardia is unclear.

METHODS

We therefore retrospectively investigated 100 selected patients (25 with documented, sustained ventricular tachycardia (< 230/min) ( = VT group), 25 resuscitated from ventricular fibrillation (VF group) and 50 without ventricular arrhythmias (phi VT/VF group)) in the chronic phase after myocardial infarction. Late potential analysis was performed at rest, during atrial pacing at a rate of 100/min and 120/min (n = 60), during and after occlusion of the coronary artery for coronary angioplasty (PTCA) (n = 70), and immediately after maximum exercise using selective signal averaging.

RESULTS

At rest in 72% of patients in the VT group, in 32% of the VF group, and in 6% of the phi VT/VF group late potentials could be found. During atrial pacing in 80% of patients in the VT group, in 72% of the VF group, and in 10% of the patients in the phi VT/VF group and during ischaemia because of occluded coronary artery in 86% of patients in and the VT group, 70% of the VF group, and in 20% of the patients of the phi VT/VF group late potentials were present. Immediately after maximum exercise which let both ischaemia and increased heart rate, late potentials were detectable in 92% of patients in the VT group, 80% of the VF group, and in 14% of patients in the phi VT/VF group. Similar results could be achieved by using the Holter-ECG after exact correction of recorder tape speed variations. 62% of patients with only by ischaemia, increased heart rate or exercise provokable late potentials and all patients with preexistent not by PTCA extinguished late potentials developed recurrent ventricular tachycardias during the one year follow-up period. Patients without late potentials (n = 50) and patients with preexistent by PTCA extinguished late potentials (n = 11) had no recurrent ventricular tachycardias. Cycle length of recurrent and clinical tachycardia in patients with preexistent not by PTCA extinguished late potentials (n = 18) were significantly longer than in patients with only provokable late potentials (n = 21).

CONCLUSIONS

Analysis of functional changes of ventricular late potentials with exercise or in Holter ECG recordings promises considerable improvement of postinfarction risk stratification especially in patients prone to ventricular fibrillation.

'True' atrial tachycardia

Atrial tachycardia is a rare form of supraventricular tachycardia, accounting for about 10-15% of patients presenting to experienced arrhythmia centres for radiofrequency catheter ablation. The mechanism may be either focal due to increased or abnormal automaticity or triggered activity, or macro re-entrant. When incessant tachycardia is present, tachycardiomyopathy may develop. The efficacy of antiarrhythmic drugs for long-term management of atrial tachycardia is poorly defined, but is probably limited. Class IC or class I agents may be used in re-entrant atrial tachycardia, and verapamil, beta-blockers or class IC agents in the focal type. If these drugs fail, amiodarone may be tried. Experience with radiofrequency catheter ablation to cure atrial tachycardia is limited, but results are very promising with success rates between 80% and 95%, and an acceptably low recurrence and complication rate. Thus, it is likely that, with more experience, radiofrequency catheter ablation will become therapy of first choice for atrial tachycardia when this arrhythmia is not easily and effectively controlled by drugs.

[Repetitive monomorphic ventricular tachycardia (Gallavardin type): clinical and electrophysiological characteristics in 20 patients]

Repetitive monomorphic ventricular tachycardia (RMVT) is defined by the presence of numerous monomorphic isolated, premature ventricular complexes, couplets, and runs of unsustained ventricular tachycardia having the same morphology in patients without structural heart disease. Patients with RMVT mostly demonstrate the typical left bundle branch block morphology with normal or rightward axis during tachycardia. At our institution, 20 patients with RMVT have been systematically studied: a syncope had occurred in 35% of our patients, in three cases a syncope was the first manifestation of the RMVT. Of our RMVT patients, 25% developed sustained episodes (> 3 min) of ventricular tachycardia as documented by Holter ECG. The salvos of ventricular tachycardia are generally short in RMVT. This behavior and the typical exercise dependence differentiates RMVT from paroxysmal sustained idiopathic ventricular tachycardia. Exercise testing is mandatory for correct diagnosis of RMVT. In our institution, 85-90% of RMVT patients demonstrated runs of ventricular tachycardia or sustained ventricular tachycardia while on a treadmill (exercise test) or during isoproterenol infusion. RMVT was inducible by programmed electrical right ventricular stimulation in only 13% of our patients. Therefore, in patients with suspected RMVT programmed electrophysiological stimulation is only useful to differentiate a ventricular tachycardia from a supraventricular tachycardia with bundle brunch block or in patients with unexplained syncope. The prognosis is considered generally good; in our patients no life threatening ventricular tachyarrhythmias were observed during a follow-up of up to 4 years. Verapamil and beta-adrenoceptor antagonists generally offer symptomatic improvement. In some cases treatment with a class III antiarrhythmic agent is necessary. While drug-refractory paroxysmal sustained idiopathic ventricular tachycardia can be abladed with both immediate and long-term success, catheter ablation of RMVT is only rarely indicated.

Plasma endothelin-1 levels in patients with angina pectoris and normal coronary angiograms

BACKGROUND

Some patients with typical angina and electrocardiographic evidence of ischemia have normal coronary angiograms. These patients have a reduced coronary flow reserve and abnormal endothelium-dependent vasodilator responses; this syndrome is known as microvascular angina. Among endothelium-derived peptides, endothelin-1 (ET-1) is a potent vasoconstrictor and an important modulator of microvascular function.

METHODS

Plasma ET-1 was measured in 13 patients with typical angina, instrumental evidence of ischemia, and normal arteriograms and in 20 normal control subjects.

RESULTS

Mean concentration of ET-1 was 2.89+/-1.24 pmol/L in patients with angina and normal angiograms and 1.99+/-0.81 pmol/L in normal control subjects (p < 0.02). Plasma levels of ET-1 values were significantly higher in patients with angina, positive exercise test results for ischemia, and normal coronary arteriograms compared with the group of patients with no clinical or instrumental evidence of ischemia.

CONCLUSIONS

This is consistent with the hypothesis that in patients with microvascular angina, an endothelial dysfunction in the coronary vascular area caused by impaired endothelium-derived ET-1 could play an active role in the disease process.

[Electro-anatomic mapping of the sinoatrial activation: initial experiences with the new CARTO mapping system]

Prerequisite for successful radiofrequency catheter ablation on tachycardias is the exact mapping during the electrophysiologic study. The new mapping system CARTO allows a three-dimensional color-coded electroanatomic map of impulse propagation using electromagnetic technology. Mapping of sinuatrial activation in the right atrium of 11 patients represents the first clinical experience with this new system. The physiological activation sequence could be determined in all patients three-dimensionally, and the sinus node could be localized as a physiological activation focus with interindividual variability only in the sagital plane without complications. The nonfluoroscopic mapping system allows high resolution visualization of electrical activity and may therefore improve precision and simplify the determination of the arrhythmogenic substrate during tachycardias for successful catheter ablation.

Influenza A outbreak among adolescents in a ski hostel

An outbreak of influenza A H3N2 with a high attack rate (49%) and abrupt onset (69% became ill within 2 days) occurred among 81 ski school participants who stayed in a crowded hostel in Austria in early 1997. Two students were hospitalized with pneumonia; one of them died. Cultures of blood and/or respiratory secretions from the hospitalized students yielded toxin-producing Staphylococcus aureus. Influenza A H3N2 was confirmed serologically in four participants, including one surviving hospitalized student, and by polymerase chain reaction of lung tissue from the deceased student. This investigation demonstrates that influenza can cause an explosive outbreak among skiers in a crowded hostel, leading to severe complications among previously healthy adolescents.

[Epidermal growth factor (EGF) in tears in excimer laser photorefractive keratectomy. Responsible for postoperative refraction and "haze"?]

BACKGROUND

Corneal wound healing is of critical importance for the postoperative outcome of excimer laser PRK. Wound healing is a complex biological process that is well characterised at the microscopic level, but its regulation is poorly understood at the molecular level. Among various cytokines, epidermal growth factor (EGF) plays an important role in superficial wound healing. The synthesis of EGF varies individually; therefore, by determining the EGF concentration in the tear fluid, patients with increased wound healing activity might be traced.

METHODS

In this study we measured the EGF concentration pre- and postoperatively in the tear fluid of 50 eyes using a ELISA test. The preoperative refraction was between -2.00 and -10.00 dioptres. The maximum follow-up was 6 months.

RESULTS

Preoperatively, in all eyes the EGF concentration in the tear fluid was between 0.2 and 1.7 ng/ml. In contrast, 1 week postoperatively, these values increased (0.21-22.50 ng/ml); 4 weeks postoperatively, the EGF concentration was in all eyes back to preoperative levels. In eyes with high EGF tear fluid concentration 1 week after surgery, refraction at 6 months was outside the intended correction of +/- 1.0 D. We could not find any correlation between EGF concentration and "corneal haze".

CONCLUSIONS

EGF may play an important role in postoperative wound healing after excimer laser PRK. Investigations concerning a pharmaceutical control of EGF should be undertaken.

The combined transvenous implantation of cardioverter defibrillators and permanent pacemakers

We developed criteria for implantation and programming of permanent endocardial pacemakers in patients with a nonthoracotomy ICD system. These criteria were prospectively used in 10 patients who recieved an ICD prior to (n = 5) or following (n = 5) implantation of a dual chamber (n = 6) or ventricular (n = 4) pacemaker with a unipolar (n = 4) or bipolar (n = 6) lead configuration. All patients were tested for interactions or malfunctions. Undersensing of ventricular fibrillation by the atrial sense amplifier and inadequate atrial pacing occurred in one patient with a unipolar dual chamber system programmed to AAIR but didn't impair ICD sensing. Transient or permanent loss of capture or sensing of the pacemaker was not observed after ICD shocks with the output programmed to double pulse width and voltage of stimulation threshold and the sensitivity to 50% of the detected R wave. One episode of transient reprogramming occurred without clinical consequences. One unipolar ventricular pacemaker lead had to be exchanged against a bipolar lead because of oversensing of the pacing artifact by the ICD. There was no failure of an ICD to detect ventricular arrhythmias due to inadequate pacemaker activity. During a follow-up period of 21 +/- 11 months, a total of 78 ventricular arrhythmias were effectively treated in six patients. Thus, a combined use of transvenous ICD and pacemaker is possible despite the close vicinity of pacing and defibrillations leads. Optimized programming different to the common settings is required. As interactions occurred only in unipolar pacemaker leads bipolar systems should be used in these patients.

The positive charge of the imidazole side chain of histidine7 is crucial for GLP-1 action

Glucagon-like peptide-1(7-36)amide/(7-37) (GLP-1) is an incretin hormone which plays an important role in postprandial glucose homeostasis. Since GLP-1 potentiates glucose-induced insulin secretion, stimulates insulin biosynthesis and inhibits glucagon release, it is a potential tool for the treatment of diabetes mellitus. For this, an exact understanding of the structural/functional moieties of the peptide is mandatory. The present study investigates the importance of structural features of histidine7 at the N-terminus for GLP-1 action. Based upon binding and activity data obtained from ten different GLP-1 analogues we show that not the positive charge of the free alpha-amino group but the positive charge of the imidazole side chain of histidine is crucial for GLP-1 action. The presence of a ring structure and a basic function as well as the correct positioning of both seems to be decisive.

Pentobarbital decreases the gamma-aminobutyric acidA receptor subunit gamma-2 long/short mRNA ratio by a mechanism distinct from receptor occupation

Treatment with pentobarbital of primary cultured cerebellar granule cells decreased the gamma-aminobutyric acid, (GABA)A receptor subunit gamma-2 long/short (gamma-2L/S) mRNA ratio. A high dose of pentobarbital (500 microM) decreased the gamma-2L/S ratio by 64%; the decrease was dose and time dependent and reversible. (-)-Hexobarbital (500 microM), the less potent stereoisomer for GABA(A) receptor activation, decreased the ratio slightly (30%) but significantly more than (+)-hexobarbital (20%). Other GABA(A) receptor activators had no (100 mM ethanol) or little (2 microM 5alpha-pregnane-3alpha-ol-20-one) effect on the gamma-2L/S ratio. Furthermore, picrotoxin (10 microM), which blocks the GABA- and pentobarbital-activated GABA(A) receptor channel, neither changed the gamma-2L/S ratio nor blocked the pentobarbital-induced changes. These data suggest that barbiturates alter the gamma-2L/S mRNA ratio by a mechanism that does not require GABA(A) receptor activation. The gamma-2L/S subunit mRNA includes an exon encoding an octapeptide that contains a protein kinase C phosphorylation consensus site. This exon-encoded peptide, occurring in the putative intracellular loop, can be phosphorylated, and in vitro, this phosphorylation has been shown to have functional consequences. This is the first report of a drug-induced alteration in receptor mRNA splicing. Furthermore, the changes in the gamma-2L/S ratio produced by pentobarbital exposure may have significant effects on the function of an important brain protein, the GABA(A) receptor.

Cyclic AMP, a possible regulator of glycolysis in the ectomycorrhizal fungus Amanita muscaria

The amounts of cyclic AMP (cAMP), fructose-2,6-bisphosphate (F26BP), trehalose and glycogen were determined in cell suspension cultures of the ectomycorrhiza-forming fungus Amanita muscaria (L. ex Fr.) Hooker. For the assay of cAMF a protocol was developed that enabled the detection of as little as 50 fmol of this secondary messenger by an enzyme-linked immuno assay (EIA). Values varied from < 1 and up to 5 pmol cAMP mg¹ d. wt according to the age of the fungal culture. Typically, a transient increase in cAMP occurred after c. 4 d of culture of the fungus on glucose-containing medium. This increase (up to 100%) was followed by the start of the logarithmic growth phase, and by a more persistent increase in F26BP. In parallel, glucose in the medium started to decrease, whilst the amounts of fungal carbohydrates, especially the disaccharide trehalose, increased, From these data we assume that a high initial rate of glucose uptake caused an increase in the fungal pools of storage carbohydrates and, via activation of an adenylate cyclase, of cAMP. According to data reported for yeast cells this should enhance the formation of F26BP by phosphorylation of relevant enzymes. In animal and yeast cells an increase in the concentration of F26BP stimulates glycolysis by activation of the ATP-dependent phosphofructokinase (PFK). A. muscaria also possesses an F26BP activated PFK and, under conditions of symbiosis, host-derived carbohydrates are supplied mainly in the form of glucose. The implications of these findings to the regulation of carbohydrate metabolism of symbiotic plant root/fungus structures (ectomycorrhiza) are discussed.

Influence of anodal electrode position on transvenous defibrillation efficacy in humans: a prospective randomized comparison

Nonthoracotomy lead systems for implantable cardioverter defibrillators (ICDs) have reduced operative mortality and morbidity as compared to epicardial lead systems but are usually associated with higher defibrillation thresholds (DFTs). The purpose of this prospective randomized trial was to investigate if the second defibrillation electrode in the left subclavian vein can increase defibrillation efficacy and decrease DFT as compared to the superior vena cava (SVC) position in nonthoracotomy lead systems for ICDs. Seventeen patients (mean age: 49.9 +/- 11.3 years, mean ejection fraction: 46.1% +/- 15.8%) were implanted with an investigational unipolar electrode (Medtronic 13001) used as the defibrillation anode. DFT testing was started in the SVC (n = 10, group A) or the left subclavian vein (n = 7, group B), and repeated in the alternative position starting at the DFT of the initial position. Fifteen patients were eligible for analysis (group A: n = 9, group B: n = 6). With the electrode in the SVC, ventricular fibrillation could be successfully terminated in 9 out of 15 patients (60%). In the left subclavian vein the success rate was 100% (P < 0.01). Mean DFT in the SVC was 13.0 +/- 5.2 J and in the left subclavian vein 10.2 +/- 4.9 J. DFTs in the left subclavian vein were either lower (group A: n = 5/9, group B: n = 5/6) or equal to the results in the SVC position (P < 0.001). Thus, the left subclavian vein appears to be a superior alternative for positioning of the defibrillation anode as compared to the SVC for nonthoracotomy lead systems using two separate leads.

Degree of carotid artery stenosis. Comparison of selective and non-selective angiographic findings with surgical specimens

OBJECTIVE

To compare the degree of vessel narrowing seen on selective and non-selective carotid artery catheter angiograms using criteria set by NASCET and ECST with the results obtained from corresponding surgical specimens.

SUBJECTS

In 40 preoperative angiograms (20 non-selective, 20 selective) the 'distal' degree of internal carotid artery (ICA) stenosis according to NASCET criteria and the 'local' degree of stenosis according to ECST criteria was assessed. These data were compared with the 'distal' and 'local' degree of ICA stenosis obtained by measuring the specimens and the diameter of the distal ICA intraoperatively.

RESULTS

The median 'local' degree of stenosis was 86.5% in the specimen and 83.5% in the selective angiograms (difference not significant). In non-selective angiography the median 'local' degree of stenosis was 77.5% compared to 84% in the corresponding specimens (P < 0.01). The median 'distal' degree of stenosis in selective angiography was 76.5 versus 75.5% in the specimens (n.s.). The median 'distal' degree of non-selective angiography was 67% compared to 77.5% in the corresponding specimens (P = 0.02). The trend to underestimate high grade stenosis (above 90%) was more pronounced in non-selective than in selective angiography. Medium grade stenosis (60-80%) was slightly overestimated in selective angiography.

CONCLUSION

Selective angiography is more accurate in determining the 'true' degree of stenosis in internal carotid artery disease, taking into account a slight overestimation of medium grade stenosis. High grade stenosis is underestimated in both selective and non-selective angiography. These observations extend to both the ECST and NASCET criteria of measuring the degree of stenosis, which differ by about 10%.

[Effect of collateral circulation on myocardial perfusion using thallium-201]

BACKGROUND

The influence of collateral circulation (CC) on thallium-201 myocardial uptake was studied in 69 patients with coronary artery disease who underwent a coronary angiography.

MATERIALS AND METHODS

According to Cohen and Rentrop a CC of 2nd and 3rd degree only was considered. A stress-early redistribution 201Tl scintigraphic protocol was utilized. The images were divided into five segments in each projection; the segments with higher uptake were considered as normal (100%). 1035 segments were analyzed and each segment was related to the donor artery on the basis of the 201Tl and angiographic evaluation. Patients were distinguished in single or multi-vessel disease with or without CC. In collateralized segments related to occluded or functionally more severe coronary stenosis, a somewhat significant prevalence of normal thallium-201 perfusion was observed, while in the non collateralized segments a higher prevalence of irreversible thallium defects was observed.

CONCLUSIONS

The data suggest that CC is one of the factors responsible for the presence of normal scintigraphic images in patients with severe coronary stenosis or complete occlusion.