Rate-dependent effects of ajmaline and propafenone on atrioventricular conduction.

The aim of the present study was to characterize the time dependence of the depressant effects of ajmaline and propafenone on the Ca(2+)-channel-dependent tissue of the atrioventricular node in isolated guinea pig hearts perfused by the method of Langendorff. Ajmaline at a concentration of 0.03 microM and propafenone at a concentration of 0.3 microM caused a significant and comparable prolongation of the His bundle and atrioventricular conduction time (AVCT). When the pacing cycle length was abruptly shortened from 240 to 180 ms, the mean time constant (tau on) of the rate-dependent AVCT prolongation was comparable for ajmaline and propafenone. In contrast, if the pacing cycle length was abruptly increased from 180 to 240 ms the mean time constant (tau off) for ajmaline was significantly higher than for propafenone. The rate-dependent increase of the atrioventricular effective refractory period was significantly more pronounced in the presence of ajmaline than of propafenone. Ajmaline and propafenone affect the Ca(2+)-channel-dependent tissue of the myocardium. The more pronounced rate-dependent effect of ajmaline on the atrioventricular effective refractory period may be explained by a slower dissociation kinetic from the channel.

Effects of semotiadil, a novel Ca2+ channel antagonist, on the electrical activity of Langendorff-perfused guinea pig hearts in comparison with diltiazem, amlodipine and nifedipine.

Semotiadil, a new Ca2+ antagonist with a high vasoselectivity, in high concentrations depresses AV nodal conduction in a frequency-dependent manner. The aim of the present study was to investigate the effects of semotiadil on intact cardiac conduction and the pacemaker system in comparison with diltiazem, amlodipine and nifedipine. The effects were studied in isolated guinea pig hearts perfused by the method of Langendorff. Both semotiadil and diltiazem decreased markedly the sinus rate in a concentration-dependent manner whereas this was not the case in the presence of amlodipine and nifedipine. Semotiadil (10 microM) markedly prolonged sinus node recovery time and in the presence of diltiazem (10 microM) in 5 out of 7 experiments an intermittent sinus node arrest occurred. Atrioventricular conduction and the effective refractory period of the AV node were most affected by diltiazem and semotiadil. The Ca2+ channel blocking compound semotiadil showed the most pronounced rate-dependent effects on the AV node. In the presence of diltiazem the QT interval became even shorter than in untreated hearts. In contrast, semotiadil did not act on the QT interval. In conclusion, as semotiadil exerts a clear rate-dependent effect on AV nodal conduction with a long time constant, it mimics the electrophysiological behavior of a substance of the verapamil type.

Frequency-dependent effects of propafenone decrease with duration of ventricular tachycardia in isolated guinea pig hearts.

Na+ channel blockers terminate tachyarrhythmias primarily by rate-dependent effects. The purpose of this study was to investigate the use-dependent effects of propafenone in isolated guinea pig and rabbit hearts perfused by the method of Langendorff. In the presence of propafenone (0.3 microM) during ventricular pacing, an abrupt decrease of the pacing cycle length (220 ms to 120 ms) slowed the intraventricular conduction with a transient peak QRS prolongation of 33.8 +/- 2.0% after 5.7 +/- 0.5 s (P < 0.01) which subsequently decreased to a steady state of 14.0 +/- 2.5% after 38.0 +/- 5.5 s (mean +/- S.E.M.; n = 10; P < 0.01). The ventricular effective refractory period was significantly prolonged if evaluated by a train of 10 basic stimuli (S1) (interstimulus interval: 120 ms) followed by a premature stimulus (S2). However, when the train of basic stimuli was increased the effective refractory period diminished progressively. An initial increase in total activation time vanished with continued rapid ventricular stimulation. These effects may be explained by a shortening of the action potential during high rates resulting in a decreased binding of propafenone to Na+ channels.

Capsaicin-sensitive afferents and blood pressure regulation during pentobarbital anaesthesia in the rat.

(1) Maintenance of blood pressure was investigated during induction of pentobarbital anaesthesia in rats after elimination of capsaicin-sensitive afferent neurons (capsaicin-denervated rats) as compared to vehicle-treated controls. The catecholamine content of heart and adrenals and the rise in blood pressure following electrical excitation of the spinal adrenergic nerves (pithed rat preparation) was also compared between both groups. (2) Capsaicin-denervated rats and their controls had equal amounts of catecholamines in heart and adrenals as well as equal pressor responses to electrical stimulation of spinal sympathetic nerves, thus excluding an influence of capsaicin on efferent pathways. In the state of consciousness, both groups showed the same blood pressure. (3) In capsaicin-denervated rats and in their controls, pentobarbital-induced anaesthesia (50 mg/kg i.p.) was characterized by a decline in blood pressure during the first 6 min. In the controls, this fall in blood pressure was followed by a slow compensatory rise to a level slightly higher than before anaesthesia, and this level was maintained during the following 60 min. This compensation was completely absent in capsaicin-denervated rats, indicating a role for capsaicin-sensitive nerves in this mechanism. An injection of pentobarbital (50 mg/kg i.p.) in pithed rats reduced the pressor response to electrical stimulation of spinal sympathetic nerves by about 40% in capsaicindenervated rats and in their controls. This inhibitory effect of pentobarbital might be involved in the initial fall in blood pressure in intact animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of endothelin on the cardiovascular system and on smooth muscle preparations in different species.

(1) The actions of porcine endothelin (ET), an endothelium-derived vasoconstrictor peptide, have been investigated in several in vitro smooth and cardiac muscle preparation as well as on the blood pressure of anaesthetized rats and rabbits. (2) In isolated visceral smooth muscles (guinea pig ileum, rat colon and uterus, rabbit jejunum) ET caused a long-lasting contraction which persisted after repeated rinsing. ET did not interfere with the spontaneous phasic activity of the rabbit jejunum or with contractions evoked by histamine or carbachol. (3) ET contracted isolated blood vessels (portal vein of guinea-pig and rat). In isolated perfused organs (rabbit ear, guinea-pig lung, rat mesentery and hindpaw) ET led to a long-lasting vasoconstriction. In the isolated perfused guinea-pig lung ET caused vaso- and bronchoconstriction. (4) ET produced a long-lasting positive inotropic effect in spontaneously beating isolated guinea-pig atria. The positive inotropic action of strophanthin was augmented in the presence of ET. (5) In the isolated perfused guinea-pig and rat hearts the prominent effect of ET was a long-lasting coronary vasoconstriction. (6) Pithed rats responded to i.v. injection of ET with a long-lasting increase in blood pressure. In pentobarbitone anaesthetized rats pretreated either with atropine, with guanethidine plus atropine, or with guanethidine plus atropine plus indomethacin, the long-lasting increase in blood pressure was smaller than in pithed rats whereas the initial short-lasting decrease in blood pressure was more pronounced; in pentobarbitone anaesthetized rabbits endothelin caused bronchoconstriction, a decrease in blood pressure and a pronounced increase in central venous pressure possibly resulting from pulmonary or coronary artery constriction or a combination of both effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of rate-dependent effects of verapamil, diltiazem, and digoxin on atrioventricular conduction.

The calcium channel blocking agents, verapamil and diltiazem, and the digitalis compound, digoxin, caused drug specific rate-dependent changes of the atrioventricular conduction time (AVCT). The purpose of this study was to investigate this rate adaptation of the AVCT in isolated guinea pig hearts perfused by the method of Langendorff to get an insight in drug-specific binding kinetic to the respective channel. In the presence of 10 nM verapamil, 30 nM diltiazem, or 0.6 nM digoxin, the atrioventricular conduction time was prolonged to a comparable degree during sinus rhythm. The drug-specific time constant, characterizing the rate-dependent adaptation of the AVCT, in the presence of a substance was comparable if evaluated after abruptly changing the heart rate from the pacing cycle length of 240 ms to 180 ms (tau-on) or from 180 to 240 ms (tau-off). The adaptation of the AVCT in the presence of verapamil (tau-on = 178 +/- 45 beats, tau-off = 125 +/- 33 beats, mean +/- SEM) was more pronounced than in the presence of digoxin (tau-on = 144 +/- 24 beats, tau-off = 98 +/- 15 beats) or diltiazem (tau-on = 70 +/- 11 beats, tau-off = 98 +/- 15 beats). In conclusion, the differences in the rate adaptation of the AVCT may be explained by the drug-specific association and dissociation kinetic to the calcium channel, slow in the case of verapamil, and fast in the case of dilitiazem, whereas this phenomenon in the presence of digoxin may be explained by its direct effects on passive membrane properties.

Effects of verapamil and diltiazem on the ventricular rate during simulated atrial flutter in isolated guinea pig hearts.

To compare the direct effects of verapamil and diltiazem on the ventricular rate during atrial flutter, we developed an atrial flutter model in guinea pig isolated hearts. Atrial flutter was simulated by rapid atrial pacing (cycle length = 50 ms). At this atrial pacing cycle length, the shape of the frequency of distribution of the ventricular cycle lengths was comparable to that during spontaneous atrial flutter. Verapamil (0.01, 0.03 microM) and diltiazem (0.03, 0.09 microM) caused a comparable prolongation of the atrioventricular conduction time and atrioventricular refractoriness. Also, the anterograde Wenckebach cycle length was increased to a comparable degree by both substances. The mean ventricular cycle length during atrial flutter was comparable prolonged by both substances. The prolongation of the maximal ventricular cycle length was significantly more pronounced in the presence of verapamil. The time dependence of drug-induced alterations in atrioventricular conduction time during abrupt changes of heart rate is significantly more pronounced in the presence of verapamil compared to diltiazem. In conclusion, the more pronounced effect of verapamil on the maximal ventricular cycle length compared to the action of diltiazem may be explained by the slow binding kinetic of this drug to the Ca2+ channel resulting in a longlasting blockade of the Ca2+ channel.

A comparison of the effects of adenosine and verapamil on the conduction and pacemaker system of isolated guinea pig hearts.

Adenosine and verapamil are effective in the treatment of supraventricular arrhythmias. Also, both substances can provoke sinus node arrest or a third-degree atrioventricular (AV) block with a ventricular escape rhythm. The aim of this study was to compare the effects of adenosine and verapamil on sinus rate and on the rate of the ventricular escape rhythm while a third-degree AV block was induced by both drugs. Experiments were performed on isolated spontaneously beating guinea pig hearts perfused by the method of Langendorff. A third-degree AV block was induced by adenosine at a concentration of 30 microns and by verapamil at a concentration of 1 micron. Adenosine (30 microns) reduced sinus rate only moderately whereas it nearly halved the rate of the ventricular escape rhythm compared with that produced by cutting the AV node. In contrast, verapamil left the rate of the ventricular escape rhythm unchanged but nearly halved the spontaneous sinus rate compared with control conditions. In conclusion, adenosine and verapamil given at dosages with comparable effect on the AV node have markedly different effects on different pacemakers in the same heart. In the treatment of supraventricular arrhythmias, adenosine probably should be used with great caution since it can cause a very slow ventricular escape rhythm.

[Kala-azar acquired in Croatia]. / In Kroatien erworbene Kala-Azar.

Six weeks after his return from a two-week vacation in Croatia a 52 year-old janitor from Graz complained of loss of appetite, fever, headache, and a 9-kg weight loss. The spleen was enlarged to 16cm as measured by sonography. Laboratory tests revealed pancytopenia, a prolonged prothrombin time and elevation of serum LDH concentration. While repeated bone marrow biopsy showed no signs of leishmaniasis, high antibody titers against leishmania antigen led to the diagnosis of kala-azar. The indirect immunofluorescent antibody test (1:128) and a haemagglutination-inhibition test (1:512) showed diagnostic elevations of titers. Therapy with pentostam led to prompt defervescence and resulted in a full recovery of the patient. After six weeks a marked decrease of antibody titers in the haemagglutination-inhibition test (1:16) could be observed. Leishmaniasis has to be considered in patients with fever of unknown origin who return from Mediterranean countries. Despite a negative bone marrow biopsy a diagnosis is possible on the basis of serological tests. This is important because effective therapy is available as illustrated by this patient and because of the fact that the disease runs a lethal course if the diagnosis is missed.

Carotid artery aneurysm as a rare cause for aspiration pneumonia. A case report.

A now 92-year-old patient presented in 1990 with a massive 6 x 4 x 4 cm aneurysm of the left internal carotid artery which completely occluded the left oro- and nasopharynx. The main complaint of dysphagia was not only a consequence of the narrowed pharynx but was also due to a palsy of the glosso-pharyngeal nerve and caused one to two episodes of aspiration pneumonia per year. The patient could not be operated on because the aneurysm extended to the base of the skull. Remarkably the patient never experienced a cerebral ischemic event and during a follow-up of five years the aneurysm did not increase in size and partial thrombosis of the aneurysm was never detected. Thus conservative management seems feasible, when partial thrombosis of the aneurysm can be ruled by CT-examination.

White fingers after excessive motorcycle driving: a case report.

An 18-year-old male presented with Raynaud's phenomenon which was found to be caused by occlusion of the proper palmar digital arteries on the right hand and obstruction of the superficial palmar arterial arch on the left hand. These lesions in the arteries of both hands resemble those found in patients with vibration-induced white fingers such as in mine or foundry workers. The only likely cause for the pathological vascular findings in our patient was an exposure to vibration due to excessive off-street motorcycle driving. Therapy with intraarterial prostaglandins resolved the ischemic syndrome but it promptly recurred when the patient resumed motor cycle driving. Therefore, we suggest that excessive cross country motor cycle driving may cause vibration-induced white fingers.

[Etiology of deep venous thrombosis of the leg]. / Atiologie der tiefen Beinvenenthrombose.

50% of all patients with deep venous thrombosis (DVT) are simultaneously suffering from other diseases, which might support or cause the thrombogenesis. In the other 50% no etiological factor can be identified. There are several factors predisposing to DVT, such as immobilisation, surgery, old age of the patient, estrogen treatment. These factors are risk factors but not etiological factors. DVT is not only initiated by the three main factors (hypercoagulability, stasis, endothelial lesion) already described by Virchow. A very complicated balance of several complex single systems (endothelium, vessel wall motion, thrombocytes, hemostatic and fibrinolytic systems with their inhibitors) has to be disturbed in order to initiate venous thrombosis.

A prospective evaluation of sensitivity and specificity of the ankle/brachial index in the follow-up of superficial femoral artery occlusions treated by angioplasty.

The aim of this study was to provide estimates of sensitivity and specificity of clinical history, pulses, and ankle/brachial index (ABI) in the follow-up of atherosclerotic occlusions of the superficial femoral artery treated by peripheral transluminal angioplasty (PTA). A total of 116 patients were followed prospectively for 1 year after angioplasty with follow-up visits immediately after angioplasty, and at 3, 6, and 12 months. All patients underwent digital subtraction angiography after 1 year of if they reported a deterioration of their symptoms. Reobstruction was defined as reocclusion or as restenosis exceeding 70%. Patency rates were calculated separately by clinical and ankle/brachial criteria; sensitivity and specificity were derived using angiography as standard. The presence or absence of pulses distal to the treated vessel segment had a sensitivity of 78% and a specificity of 66% for a reocclusion or significant restenosis; subjective complaints evaluated by history had a sensitivity of 83% and a specificity of 51%. The sensitivity of the ABI was 72% and 66%, with a specificity of 82% and 100% for cutoff values of 0.10 and 0.15, respectively. One year after PTA the angiographic patency rate was 39% +/- 5%; the patency rate based on ABI criteria 34% +/- 5%. A deterioration in the ABI by 0.15 indicated with reasonable certainty a reocclusion or significant restenosis whereas the sensitivity of the ABI was poor in detecting significant restenosis after PTA of occlusions of the superficial femoral artery. When only clinical criteria were used, the true patency rate was significantly overestimated as more than half of all reobstructions remained asymptomatic.

[Can vasomotion be modified by vasoactive substances or hemodilution?]. / Kann die Vasomotion durch vasoaktive Substanzen oder Hämodilution beeinflusst werden?

The maintenance of adequate local tissue perfusion is the result of control mechanisms which reside at the level of microscopic blood vessels: The constriction and relaxation of the vessels whose vascular walls are endowed with smooth muscle. This phenomenon of vasomotion guarantees homeostatic conditions in peripheral tissues. Superior disorders of homeostasis are primarily compensated by activating the vasomotion. The increase of vasomotion results in prostration of the vasomotoric activity and ends in the local biological disaster finally. Therefore an essential therapeutic strategy to avoid or remove peripheral arterial reduced or lacking perfusion is the reactivation of vasomotion. In this pilot study the effect of conservative therapeutic strategies to the vasomotion was investigated with dynamic capillaroscopy in normal perfused areas of the finger nailfold. A significant influence of buflomedil and alprostadil to the capillary blood cell velocity was found. Vasomotion was susceptible to hydroxyethylstarch and alprostadil but was influenced significantly only by buflomedil. Nevertheless we cannot conclude that the applicated substances will have a favourable effect in ischemic areas too, where maximum dilatation still exists.

Frequency-dependent effects of adenosine and verapamil on atrioventricular conduction of isolated guinea pig hearts.

Frequency-dependent depressant effects of a drug on slow channels in the atrioventricular (AV) node are important in its efficacy against supraventricular tachycardias. Verapamil terminates reentrant supraventricular arrhythmias by depressing conduction through the AV node. Similar effects have been described for adenosine. We compared the use-dependent effects of both drugs on AV nodal conduction in isolated guinea pig hearts perfused by the method of Langendorff. Adenosine 3 microM and verapamil 0.01 microM caused a comparable prolongation of AV conduction time (AVCT) and reduction in sinus rate (SR). The time dependence of drug-induced changes in AV conduction was characterized after the atrial pacing rate was changed abruptly. The basic cycle length was shortened abruptly from 240 to 180 ms. The resulting time constant for adenosine (tau = 467 +/- 187 beats, mean +/- SD) was significantly (p < 0.05) longer than that for verapamil (tau = 264 +/- 121 beats). At a pacing cycle length of 180 ms, the rate-dependent conduction slowing tended to be more pronounced in the presence of adenosine than of verapamil. Adenosine had more pronounced frequency-dependent effects on AV conduction than did the calcium channel blocker verapamil. This may explain the higher clinical efficacy of adenosine in supraventricular tachycardias in which the AV node forms a part of the reentrant circuit.

How to measure AV nodal refractoriness in the presence of verapamil, amiodarone, digoxin, and diltiazem.

On the AV node the negative dromotropic action of verapamil, amiodarone, digoxin, and diltiazem is known to be rate dependent. The effective refractory period of the AV node (AV-ERP) at a short cycle length is related to the AV conduction at that cycle length. We investigated how the number of stimuli during the conditioning train (S1) (during measurement of refractoriness at a high pacing rate [cycle length = 180 ms]) might influence the AV-ERP in isolated guinea pig hearts in a Langendorff preparation. Verapamil (10 nM), amiodarone (10 microM), digoxin (0.6 nM), and diltiazem (30 nM) caused a comparable prolongation of the AV conduction time (AVCT). All four drugs caused a significant prolongation of the AV-ERP when evaluated by a standard stimulation protocol with a conditioning train of 10 stimuli (10 S1) at a pacing cycle length of 180 ms followed by the test stimulus (S2). When the number of stimuli during the conditioning train (S1) was increased (> 10), until the prolongation of AVCT reached steady state, the AV-ERP in the presence of verapamil (132 +/- 4 vs 141 +/- 3 ms; P < 0.05, mean +/- S.E.M.) and diltiazem (143 +/- 3 vs 151 +/- 3 ms; P < 0.05) was prolonged significantly further. These results indicate that the effect of drugs on AV-ERP should be measured with a modified stimulation protocol, whereby the number of conditioning stimuli is comparable to the time constant characterizing the prolongation of AVCT at fast pacing rates.

Pulsed excimer laser versus continuous-wave Nd:YAG laser versus conventional angioplasty of peripheral arterial occlusions: prospective, controlled, randomised trial.

Early clinical studies of coronary and peripheral laser angioplasty showed that arterial occlusions could be recanalised by continuous-wave lasers delivered with contact probes and by pulsed lasers applied with multifibre catheters. However, whether laser-assisted angioplasty improves success rates in reopening occlusions and in long-term patency rates is unclear. We have compared the primary recanalisation and long-term patency rates after laser-assisted and conventional percutaneous transluminal angioplasty (PTA) of femoropopliteal artery occlusions in 116 consecutive symptomatic patients (excimer laser 37, Nd:YAG laser 40, PTA 39). Primary recanalisation was achieved in 81 patients (70%). The primary recanalisation rate achieved with the excimer laser was significantly lower than that with the Nd:YAG laser (49% vs 78%, p < 0.01) or with PTA (82%, p < 0.003). The overall angiographic recanalisation rate (primary and secondary recanalisation) after laser and PTA was 89%. After 3 months, clinical improvement was recorded in 76% of patients. Clinical long-term results were available in 94 (91%), and angiographic long-term results in 77 (75%), of 103 successfully recanalised patients. Life-table analysis of the long-term results revealed no significant difference of the restenosis rate between the three treatment groups. The 12-month patency rate was 60% as assessed clinically and 39% as judged by angiography. Primary and secondary recanalisation rates and long-term patency rates were significantly correlated with length of the occlusion. Our results suggest that PTA of femoropopliteal artery occlusions is only indicated if the occlusion is short (< 8 cm) and that laser-assisted angioplasty should only be used after failure of conventional PTA.

Comparison of the frequency-dependent effects on the atrioventricular node of verapamil, amiodarone, digoxin, and diltiazem in isolated guinea pig hearts.

To slow ventricular rate during supraventricular tachycardia, a drug must have a strong rate-dependent depressant effect on atrioventricular (AV) conduction. We investigated the frequency-dependent effects of verapamil, amiodarone, digoxin, and diltiazem on AV conduction time (AVCT) in isolated guinea pig heart perfused by Langendorff method. Verapamil (0.01 microM), amiodarone (10 microM), digoxin (0.6 nM), and diltiazem (0.03 microM) caused comparable prolongation of AVCT and also a comparable reduction in sinus rate. To evaluate the time dependence of drug-induced alterations in AVCT, we abruptly increased the atrial pacing rate and shortened the pacing cycle length (CL) from 240 to 180 ms. The resulting time constant was longest in the presence of verapamil (tau = 194 +/- 45 beats, mean +/- SEM) and the shortest during perfusion with diltiazem (tau = 89 +/- 9 beats). The magnitude of AVCT prolongation after abrupt increase in pacing rate was significantly greater for digoxin as compared with all other drugs tested. The calculated beat-to-beat increase in AVCT evaluated by dividing the magnitude of AVCT prolongation by the time constant tau was greatest with diltiazem, which may explain the high efficacy of diltiazem in controlling ventricular rate during atrial fibrillation.

A simplified procedure for intra-arterial thrombolysis with tissue-type plasminogen activator in peripheral arterial occlusive disease: primary and long-term results.

One-hundred and fifty patients with thrombotic and 60 patients with embolic occlusions of the superficial femoral and/or popliteal artery underwent a simplified IAT (intra-arterial thrombolysis) procedure. Ten mg rt-PA combined with 3000 IU Heparin were infused over 6 h, thereafter the extent of thrombolysis was checked fluoroscopically and the above mentioned treatment course repeated up to four times if necessary. The IAT regimen employed did not involve mechanical recanalization attempts; if complete thrombolysis revealed an underlying stenosis, a PTA (percutaneous transluminal angioplasty) was subsequently performed. IAT resulted in complete recanalization of 88 thrombotic occlusions (59%; 95% confidence interval: 50.8%-66.8%) and of 53 embolic occlusions (88%; 95% confidence interval: 77.1%-94.8% P < 0.001). In a further 33 (22%) thrombotic and four (7%) embolic occlusions IAT reduced the length of the occluded segment. At discharge, 102 (67%) patients with thrombotic and 55 (92%) patients with embolic occlusions were clinically improved. Overall, untoward effects occurred in 60 patients (29%): 47 (22%) were minor. Four patients (2%) suffered a systemic haemorrhage (three gastrointestinal, one macrohaematuria). The cumulative potency rate was significantly higher in patients with embolic occlusions throughout follow-up (82% vs 49% for thrombotic occlusions at 2 years, P < 0.001). Although all amputations were carried out in patients with thrombotic occlusions, follow-up mortality did not differ significantly between patients with embolic and thrombotic occlusions.

Nd:YAG laser with sapphire tip combined with balloon angioplasty in peripheral arterial occlusions. Long-term results.

In 167 patients with complete occlusion (greater than 3 cm) of the femoropopliteal artery, percutaneous transluminal laser angioplasty (PTLA) was performed after an unsuccessful attempt at crossing with a guide wire and was immediately followed by balloon dilatation. An Nd-YAG laser and an optical fiber delivery system with a sapphire tip serving as a contact probe were used for PTLA. In 132 of 167 (79%) patients, the occluded segment was successfully reopened. Clinical symptoms improved in 126 of 167 (75%) patients. PTLA was unsuccessful in 35 patients, and in 15 of these, injury of the vessel wall occurred. In one patient, surgical drainage of a large hematoma became necessary. All patients in whom recanalization had been achieved were randomized to receive long-term treatment with either phenprocumarol or acetylsalicylic acid (ASA) plus dipyridamole to prevent rethrombosis. At 36 months of follow-up, the cumulative patency rate (CPR) was 63%. A complete reobstruction in 32 patients (24%) and a partial reobstruction in 15 patients (11%) were found angiographically. The CPR after 36 months was significantly lower (p less than 0.05) in patients younger than 60 years of age (54%) than in patients older than 60 (68%); it was also significantly lower (p less than 0.05) in patients with reduced peripheral runoff (55%) due to obstructed arteries of the lower leg than in patients with unaffected runoff (73%). The CPR was 65% in recanalized segments shorter than 7 cm and was 62% in recanalized segments longer than 7 cm.(ABSTRACT TRUNCATED AT 250 WORDS)