Effects of positive inotropic stimulation on postischemic myocardium with graded dysfunction

OBJECTIVE

To investigate the effects of moderate prolonged and of maximum short-term positive inotropic stimulation of postischemic myocardium as a function of the severity of stunning.

METHODS

Stunned isolated rat hearts (n = 116) after 30 min and 45 min of ischemia were stimulated with dopamine to raise systolic function (double product) back to control levels. In the isovolumetrically beating hearts, left ventricular developed pressure, double product, dp/dtmax, coronary flow, and myocardial oxygen consumption were determined during steady-state conditions. After maximum stimulation the contractile reserve was examined. Measurements of adenine nucleotides (n = 47) and electron microscopy (n = 9) were made.

RESULTS

30 min ischemia resulted in moderate postischemic dysfunction (LVP 81 +/- 3%; P < 0.05). After 45 min ischemia, function was more severely reduced (LVP 66 +/- 5%; P < 0.01). Coronary flow tended to be lower after ischemia. Myocardial oxygen consumption was not reduced in parallel with the dysfunction. Adenine nucleotides were gradually reduced after ischemia (ATP: 2.5 +/- 0.2 and 1.2 +/- 0.1 vs. 4.2 +/- 0.2 mumol/gww; P < 0.01). Contractile reserve also decreased in relation to the previous ischemic injury (after 45 min ischemia max. LVP 105 +/- 10% vs. max. LVP 152 +/- 8% in controls, P < 0.01). Prolonged stimulation did not result in further reduction in adenine nucleotides and function.

CONCLUSIONS

Contractile reserve is decreased in postischemic myocardium in parallel with the previous ischemic burden. Depending on the degree of contractile dysfunction a disturbed function-flow-oxygen consumption relation is present. Prolonged stimulation of stunned myocardium with dopamine back to the control level of function has no harmful short-term effects, indicating sufficient mitochondrial energy generation.

Tricuspid valve endocarditis due to a jet lesion detected by echocardiography in a 27-year old man with congenital ventricular septal defect

The case of an non-addict young caucasian with isolated tricuspid valve endocarditis in congenital ventricular septal defect (VSD) is presented. Despite antibiotic treatment the patient suffered from recurrent right sided pneumonias. A computed tomography of the chest revealed an abscess localized in the right lower lung with signs of cavitation. Echocardiography identified a vegetation located at the anterior tricuspid leaflet due to a jet lesion through the VSD. ECG-gated MRI revealed normal left ventricular function and localized the septal defect and a jet against the anterior tricuspid valve leaflet. The patient underwent open heart surgery and the VSD was closed. Now, two years later, the patient is free from any symptoms or complications. This case illustrates that noninvasive techniques like echocardiography and ECG-gated MRI can not only accurately image cardiac anatomy in patients with ventricular septal defect but additionally provide information about the pathomechanism of the development of jet lesions resulting in valvular vegetations. Operative correction of underlying cardiac disease in nonaddicts with complicating tricuspid valve endocarditis might be a favourable treatment especially when antibiotic treatment fails to cure the infection.

Significance of endothelinB receptors for myocardial contractility and myocardial energy metabolism

Positive inotropy of endothelin-1 (ET-1), which has already been described in vitro, has not been detected in vivo. Combination with vasodilators has been shown to unmask a positive inotropic effect of ET-1. The ET-induced direct positive inotropy, which seems to be mediated by endothelinB (ETB) receptors, is antagonized in vivo by an indirect negative inotropy due to an ET-induced coronary vasoconstriction via ETA receptors. This study examines the significance of ETB receptors on myocardial contractility and myocardial energy metabolism. The dose-dependent hemodynamic and inotropic effects of the highly specific ETB agonist IRL 1620 (0.4, 1.0, 2.0, 4.0 nmol/kg vs. NaCl controls) were investigated in open-chest rats during and after a 7-min infusion. In addition to measurements in the intact circulation, we examined the myocardial function by isovolumic registrations independent of peripheral vascular effects. Furthermore, the effect of IRL 1620 on myocardial high-energy phosphates was studied. IRL 1620 causes a biphasic pressure response, with an initial decrease followed by a rise (differences of 0.4, 1.0, 2.0 and 4.0 nmol/kg IRL 1620 compared with the controls 5 min after infusion; mean aortic pressure: +37%, +33%, +29%, +20%). IRL 1620 has a positive chronotropic effect (HR: +2%, +14%, +16%, +6%). After an initial vasodilation, IRL 1620 augments the total peripheral resistance: +35%, +31%, +66%, +82%. Because the maximum of the isovolumic left ventricular systolic pressure (+7%, +7%, +12%, +12%) and the corresponding maximum first derivative of the left ventricular pressure (+13%, +14%, +23%, +18%) were increased under IRL 1620, these measurements indicate a positive inotropic effect of IRL 1620 in vivo. Myocardial high-energy phosphates were not changed by IRL 1620. In contrast to nonselective activation of ETA and ETB receptors by ET-1, the selective activation of ETB receptors by IRL 1620 causes a positive inotropy. This discrepancy can be explained by a less pronounced vasoconstriction with absence of myocardial ischemia after ETB receptor activation by IRL 1620.

Radiographic contrast media and the coagulation and complement systems

Intravascular contrast agents have several side effects including alterations of the hemostasis and the complement system. The effects on these systems may be one of the main causes of the "adverse contrast agent reaction." In vitro and in vivo evidence is provided that both ionic and nonionic contrast media activate the plasma kallikrein with consecutive activation of the factor XII-contact phase and stimulation of the bradykinin generation. Furthermore, activation of the complement cascade via the classic and the alternative pathways was described to a various extent for intravascular application of contrast agents. In non-reactors, these alterations are transient and only have a limited extent indicating that these reactions are within the regulatory capacity of the kallikrein-kinin-factor XII system. In reactors, however, significant evidence for an extended activation of the kallikrein system is associated with reduced levels of C1-esterase inhibitor. Therefore, patients with alterations in these systems should be regarded as candidates for adverse contrast agent reactions. Furthermore, contrast media influence the blood coagulation, especially in contact to artificial surfaces (plastic or glass). In vitro findings suggest that there is a broad scope of modifications caused by contrast agents indicating a modification of the risk of thromboembolism during angiography. Preliminary data suggest that an inhibition of clot formation is more effective with ionic compared with nonionic contrast agents. In summary, radiographic contrast agents have an impact both on the hemostasis and the complement systems. The effects may be of importance for adverse reactions as well as for thromboembolic complications during angiography.

Effect of endothelin-1 and its combination with adenosine on myocardial contractility and myocardial energy metabolism in vivo

Contradictory results have been reported about the inotropic effects of the vasoconstrictive peptide endothelin-1 (ET-1). In contrast to in vitro experiments, in vivo studies could not demonstrate a positive inotropy of ET-1. It may be possible, that the direct positive inotropic effect of ET-1 observed in in vitro studies is counterbalanced in vivo by an indirect negative inotropy due to its coronar-constrictive effect. This study examined the hemodynamic and inotropic effects of 2500 ng ET-1/kg without and after pretreatment with the vasodilating nucleoside adenosine (0.5, 2.0, 5.0 mg ADO/kg/min). Data were compared with NaCl controls in open-chest rats during and after a 7-min infusion. Besides measurements in the intact circulation isovolumic measurements were carried out for quantification of myocardial contractility independently of peripheral vascular effects. We further examined the effect of ET-1 and its combination with 2.0 mg ADO/kg/min on myocardial high-energy phosphates (ATP, AMP, ADP, creatine phosphate). ET-1 causes a strong and longlasting vasoconstriction (+ 186% v preinfusion values), which is dose-dependently antagonized in part by ADO (+ 109%, + 136%, + 60%). While the maximum of the isovolumic LVSP (peak LVSP) and the corresponding dP/dtmax (peak dP/dtmax) were unchanged with sole ET-1 (peak LVSP: +5%, peak dP/dtmax: -2%), these indexes of myocardial contractility were increased after pretreatment with ADO (peak LVSP: +11%, +13%, +4%; peak dP/dtmax: +9%, +20%, +10%) indicating a positive inotropic effect of ET-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Lower cardiac troponin T levels in patients undergoing cardiopulmonary bypass and receiving high-dose aprotinin therapy indicate reduction of perioperative myocardial damage

Nowadays in many European heart centers the activation of the fibrinolytic system, always occurring during cardiopulmonary bypass, is routinely reduced by high-dose application of the proteinase inhibitor aprotinin (total of > 4 million KIU). In this study parameters of myocardial ischemic injury were investigated with the aim of identifying further benefits of aprotinin, particularly the protection of the myocardium during the ischemic period of aortic crossclamping. Forty patients with coronary artery disease who underwent aorta-coronary bypass grafting were randomly and in a double-blind fashion divided into two groups, one that received high-dose aprotinin therapy and one that received only saline solution. Markers such as troponin T, with high specificity for detection of myocardial ischemia and infarction, and markers with more general specificity such as creatine kinase, its isoenzyme, and lactate dehydrogenase showed significantly increased values after ischemia in both groups. In patients who received high-dose aprotinin therapy 3 days after cardiopulmonary bypass all parameters measured showed significantly lower levels compared with those in the control group. Therefore we can presume that the application of high-dose aprotinin provides myocardial protection from perioperative ischemic injury.

Alterations of coagulation and fibrinolytic and kallikrein-kinin systems in the acute and postacute phases in patients with unstable angina pectoris

BACKGROUND

Unstable angina pectoris is frequently associated with intracoronary thrombus formation. In a prospective study, we investigated in 35 patients with unstable angina pectoris markers of coagulation and the kallikrein-kinin and fibrinolytic systems in the acute and postacute phases.

METHODS AND RESULTS

We determined serially in the patients up to 10 days after admission factor XII and the beta-factor XIIa inhibition, kallikrein-like activity, prekallikrein, C1-esterase inhibitor, kallikrein inhibition, high molecular weight kininogen as indicators of the contact phase and bradykinin generation, thrombin-antithrombin III (TAT) complex as marker of the activated coagulation cascade, fibrinogen, plasminogen, plasminogen activator inhibitor-1 (PAI-1), tissue-type plasminogen activator (TPA), and D-dimers as indicators of the fibrinolytic system. Data were compared with those from control subjects (n = 25) and from patients with stable angina pectoris (n = 25). In patients with unstable angina pectoris, initially the contact phase and the kallikrein-kinin system were markedly elevated (factor XII, 96 +/- 5% versus 117 +/- 5%; kallikrein-like activity, 35.7 +/- 2.9 versus 27.4 +/- 1.3 U/L; high molecular weight kininogen, 52.7 +/- 5.2% versus 87.7 +/- 3.9%; P < .01 versus control subjects). Contact-phase activation persisted for the following 10 days, whereas the initially enhanced bradykinin generation normalized after 2 days. Furthermore, we had evidence of a hypercoagulative state (TAT, 10.9 +/- 3.1 versus 4.5 +/- 0.7 micrograms/L, P < .05; D-dimer, 474 +/- 81 versus 272 +/- 71 ng/mL) persisting longer than the clinically symptomatic period in association with disturbed fibrinolysis (TPA, 15.9 +/- 1.9 versus 5.1 +/- 0.4 ng/mL; P < .01; PAI-1, 9.9 +/- 2.6 versus 4.6 +/- 1.6 AU/mL; P = NS) in the presence of elevated fibrinogen levels.

CONCLUSIONS

Our data indicate that in patients with unstable angina pectoris, intracoronary thrombus formation is associated with a hypercoagulative state, including activation of the contact phase and of the kallikrein system and increased bradykinin generation. The persistence of this hypercoagulative state, together with a disturbed fibrinolysis, might indicate an increased risk for further coronary events.

Effects of the Na+ antagonist cibenzoline on left ventricular function of postischemic hearts

The negative inotropic effect of antiarrhythmic drugs is a major drawback in antiarrhythmic drug therapy, especially in patients with reduced contractile function of the left ventricle. The circulatory and myocardial effects of the new class I antiarrhythmic drug (a Na+ antagonist), cibenzoline (2 mg/kg i.v.), were investigated in 47 open-chest rats with normal and postischemic myocardium (3 x 4 minutes of global ischemia). Hemodynamic measurements in the intact circulation and isovolumic registrations (peak isovolumic left ventricular systolic pressure and peak isovolumic dP/dtmax) were compared to saline controls. In rats with postischemic myocardium, cibenzoline caused a significant (p < 0.001) decrease in the cardiac output for 38%, in the dP/dtmax for 30%, and in the peak isovolumic dP/dtmax for 19% at the end of infusion (compared to the control). The heart rate was reduced by 22% (p < 0.001), the mean aortic pressure by 22% (p < 0.001), and the calculated systemic resistance by 20% (p < 0.001). In contrast to the results with postischemic myocardium, no important changes in the hemodynamics were detectable after an identical dose in normal animals without left ventricular dysfunction. The results indicate that standard doses of the Na+ antagonist cibenzoline may induce significant cardiodeperessant effects on postischemic left ventricles with reduced function.

[Perfusion of the left ventricular myocardium in patients with aortic valve diseases using single photon emission computerized tomography]

To determine resting myocardial perfusion in 30 patients with aortic valve disease (AVD) TI-201 emission computer tomography (ECT) studies and heart catheterization were performed. 16 patients had a predominant aortic regurgitation (AR); an aortic stenosis (AS) was found in 14 patients at catheterization. Perfusion defects were documented in 10 of 16 patients with AR, and in 5 of 14 patients with AS. Regional determination demonstrated in 10 of these 15 abnormal cases at least one of the perfusion defects in the postero-basal segment. In patients with aortic valve disease and normal myocardial perfusion scintigraphy, the ejection fraction (EF) was significantly higher (p < 0.05) as compared to the patients with abnormal TI-201 ECT (EF 65.2 +/- 15.0% vs. 58.9 +/- 15.1%). Additionally, in the 15 patients with abnormal TI-201 ECT, the left ventricular end-diastolic volume index (LVEDVI) and the left ventricular end-systolic volume index (LVESVI) were both increased (LVEDVI in AVD: 130.3 +/- 15.3 ml/m2 vs. 107.4 +/- 13.6 ml/m2, LVESVI in AVD: 61.9 +/- 14.6 ml/m2 vs. 48.0 +/- 9.8 ml/m2). In conclusion, left ventricular perfusion defects at rest can be detected by TI-201 ECT in many patients with aortic valve disease. Such myocardial perfusion defects indicate left ventricular enlargement and impaired left ventricular function, especially in patients with aortic regurgitation.

[Diagnosis of pseudoaneurysm of the ascending aorta after implantation of a valved conduit by multiplane transesophageal echocardiography]

In a 48-year-old male patient with Marfan syndrome who underwent composite graft replacement of the ascending aorta and the aortic valve with reimplantation of the coronary arteries a cardiac enlargement was detected by routine chest x-ray. Transthoracal echocardiography showed a pseudoaneurysm around the composite graft. The examination with a multiplane transesophageal echocardiographic probe demonstrated a systolic-diastolic jet into the pseudoaneurysm with the site of origin at the ostium of the right coronary artery.

Primary systemic amyloidosis leading to advanced renal and cardiac involvement in a 30-year old man

The case of a 30-year-old man with primary systemic amyloidosis is reported. Three months prior to admission the patient developed fever, night sweats, dyspnea, and bilateral ankle swelling. Recurrent left-sided pleural effusion led to further investigation when massive proteinuria with free monoclonal lambda chains in the urine became evident. Abdominal subcutaneous fat aspiration and renal biopsy confirmed the diagnosis of amyloidosis. Bone marrow biopsy and bone scan did not reveal multiple myeloma. Echocardiography showed a sparkling texture of the interventricular septum. Pulsed-wave Doppler recording of the left ventricular inflow profile showed the pattern of advanced cardiac amyloidosis consistent with markedly impaired diastolic heart function. Electrocardiogram-gated magnetic resonance imaging was carried out for noninvasive evaluation of cardiac function. The patient was started on repeated courses of melphalan, prednisone, and colchicine therapy. Despite increasing deterioration of renal function the therapy was tolerated quite well, and the patient is still alive 10 months after initial diagnosis. Although very rare in this age, primary systemic amyloidosis should be considered as a cause of pleural effusion, proteinuria, and congestive heart failure and should lead to further investigation.

Myocardial perfusion and left ventricular function early after successful PTCA in 1-vessel coronary artery disease

Myocardial perfusion (201TI-ECT) and contractile function (99mTc-ventriculography) were studied during exercise and rest 3 to 6 days after PTCA in 20 patients (11 with stable and 9 with unstable angina pectoris). All patients had single vessel disease and no previous myocardial infarction. During exercise after PTCA the ejection fraction increased for 3 to 5% and no regional wall motion abnormalities, ST-segment depression or perfusion defects occurred (with exception in one patient with very early restenosis). Therefore, perfusion and wall motion were completely normalized at rest and during exercise within days after technically successful PTCA even in patients with previously unstable angina pectoris. Pathological stress test results after this time should thus be attributed to other causes e.g. early restenosis, multivessel disease, false positive tests) and are not due to the specific situation early after PTCA.

[Comparison of the negative inotropic properties of nifedipine and nisoldipine using isovolumetric contractile parameters of the rat in vivo]

The vasoselectivity of new dihydropyridine calcium antagonists is much higher as compared to their prototype substance nifedipine. To investigate whether an equihypotensive dose of a new dihydropyridine has less negative inotropic properties in an intact circulation, nifedipine (NIF) and nisoldipine (NIS) were infused intravenously in an open-chest, anaesthetized rat model. The maximal isovolumic left ventricular pressure (LVPiso) and the maximal isovolumic rate of change of LV-pressure (dp/dtmaxiso) were determined to achieve load independent parameters of LV contractility. To evaluate the effect of the infused volume, the stability of the preparation and the hemodynamic effects of the drug-solvent, two groups with either infusion of isotonic NaCl-solution or 20% ethanol served as controls. NIF and NIS were infused in three equihypotensive doses within 7 min (NIF 250, 500, 1000 micrograms/kg; NIS 12.5, 25, 50 micrograms/kg). The decrease of the peripheral resistance of these doses was 74 +/- 6, 67 +/- 6, and 58 +/- 7% for NIF, and 78 +/- 7, 65 +/- 8, and 56 +/- 7% for NIS (p < 0.001 for all groups). In the control groups the afterload remained unchanged. NIF-infusion resulted in a dose-dependent decrease of LVPiso at the end of the infusion period (in percent of controls: NIF250 88 +/- 3%, p < 0.001; NIF500 74 +/- 3%, p < 0.001) as well as 15 min after the end of the infusion. In the same way dp/dtmaxiso decreased significantly after NIF at the end of infusion (NIF 250 82 +/- 6%, p < 0.001; NIF500 61 +/- 8%, p < 0.001) and 15 min after the end of the infusion. After NIS-infusion the contractility parameters decreased slightly after the higher dosage (25 micrograms/kg) at the end of the infusion period only (LVPiso 96 +/- 3%, p < 0.01; dp/dtmaxiso 93 +/- 5%, p < 0.01). There was no depressive effect on the isovolumic contractility parameters at the end of infusion of the lower dosage and 15 min after the drug-infusion of all dosages of NIS. Therefore, nisoldipine, as an example of a new dihydropyridine, has significantly less negative inotropic properties over a wide range of doses as compared to nifedipine in equihypotensive doses.

Activation of leukocytes and of the kallikrein-kinin system in patients with unstable angina pectoris

We investigated the leucocyte-elastase and the activity of the kallikrein system including kinin precursors and plasma inhibition levels in 14 patients with unstable angina pectoris (normal or only slightly elevated creatinine kinase levels; no transmural myocardial infarction) and compared them with 10 controls. Leucocyte-elastase levels and activity of the kallikrein system were significantly elevated in unstable angina pectoris. The bradykinin precursor high-molecular-weight kininogen was markedly decreased to 79 +/- 16% indicating kinin generation. Except for a slight decrease in the beta factor XIIa inhibition, we observed no abnormalities in the plasma kallikrein inhibition or in the antithrombin III levels in patients with unstable angina pectoris. The findings indicate a significant activation of the plasma kallikrein-kinin system, which is not associated with a considerable reduction in the plasma inhibitor levels. Kinin generation might influence vascular tone and leucocyte function and thus be involved in the pathophysiologic alterations occurring in patients with recurrent angina at rest.

Hemodynamic and inotropic effects of endothelin-1 in vivo

Endothelin-1 (ET-1) is known to have strong vasoactive properties. Contradictory results have been reported with regard to its inotropic effects. This study examined the dose-dependent (500, 1000, 2500, 5000 and 10,000 ng ET-1/kg vs. NaCl controls) hemodynamic and inotropic effects of ET-1 in 53 open-chest rats during and after a 7-min infusion. Besides measurements in the intact circulation the myocardial function was examined by isovolumic registrations independent of peripheral vascular effects. A transient ET-1 induced (500, 1000, 2500, 5000 ng ET-1/kg) decrease of the left ventricular systolic pressure (LVSP) and the mean aortic pressure (AoPmean) was followed by a dose-related rise of these pressures (LVSP: -1%, -1%, +8%, +16% vs. preinfusion values; AoPmean: -11%, +9%, +39%, +52%). Heart rate (HR) was not influenced by ET-1. Due to the dose-dependent decrease of the stroke volume (SV) the cardiac output (CO) was reduced (CO: -8%, -23%, -40%, -50%). After an initial vasodilatation ET-1 elevates the total peripheral resistance (TPR: -1%, +49%, +139%, +215%) dose-dependently. 10,000 ng ET-1/kg was a lethal dose resulting in cardiac failure within minutes (low output). Since the maximum of the isovolumic LVSP (peak LVSP) and the corresponding dP/dtmax (peak dP/dtmax) were unchanged under ET-1, the isovolumic measurements do not indicate a positive inotropic effect of ET-1 in vivo in contrast to published results of in vitro experiments. It may be possible that a direct positive inotropic effect of ET-1 observed in in vitro studies is counterbalanced in vivo by an indirect negative inotropic effect due to the coronary-constrictive effect of ET-1.

Inotropic and haemodynamic effects of d- and d,l-sotalol: comparison with other antiarrhythmics

The inotropic effects of sotalol in comparison to other antiarrhythmic drugs were tested in an experimental model allowing isovolumic measurements independently of the loading conditions. All class I drugs had a similar negative inotropic effect. d,l-Sotalol caused a dose-dependent depressant effect on the rate of left ventricular pressure development. The same held true for l-sotalol. In contrast, d-sotalol, in clinical doses, revealed no significant inotropic effects in normal hearts. In a postischemic model, d-sotalol led to a further deterioration of left ventricular function. It could be demonstrated by autonomic blockade that this effect was mainly the result of the remaining weak beta-blocking activity of the d-isomer in addition to its class III action. After intravenous administration of amiodarone in doses of 10 mg.kg-1, no significant inotropic effects were found in normal rats.

Spontaneous splenic rupture complicating acute Q fever

Q fever is usually a self-limited febrile illness that involves the lungs and the liver. Acute complications are rare. We present the case of a 30-yr-old patient with spontaneous splenic rupture during the course of acute Q fever infection. He was admitted to the hospital with high temperature and the radiological signs of an atypical pneumonia. Forty-eight hours after admission, he developed shock. Because of free intraabdominal liquid, a laparatomy was performed that revealed a tear in the enlarged spleen. A splenectomy was performed. The diagnosis of Q fever was established by a significant titer increase in complement fixation test and IgM-ELISA. Serological investigations into the patient's surroundings revealed evidence of Q fever infection in 10 additional persons. Q fever should be taken into account as a possible differential diagnosis in patients with unexplained febrile illness and symptoms of pneumonia. The acute course of Q fever infection can be complicated by splenic rupture. The diagnosis of an acute infection with Coxiella burnetii often requires serologic testing of a second serum sample obtained at least 10 days after the onset of symptoms. Q fever should be ruled out in cases of unexplained splenic rupture particularly in Q fever endemic areas.

[Hemodynamic effects of anti-arrhythmia substances]

Medical treatment of cardiac arrhythmias is limited by several side effects. Haemodynamic and proarrhythmic effects are the most important limitations of antiarrhythmic drug therapy. In this paper we present data from several studies on the haemodynamic side effects of antiarrhythmic drugs of Class I and III according to Vaughan-Williams. The results were discussed with special regard to the influence of these drugs on myocardial contractility. From the results presented it is concluded that there are no important differences in the negative inotropic effects among the Class I drugs. The clinically observed more marked cardiodepressant action of some of these drugs is probably due to their unfavourable effects on pre- and afterload of the left ventricle. From a theoretical point of view, Class III drugs should have a more favourable haemodynamic profile. However, after acute administration the commercially available Class III drugs also had a cardiodepressant action. A possible explanation for this finding might be other side effects of the Class III drugs currently available, since a pure Class III drug does not exist at present. Therefore, the special haemodynamic profile of each drug should be taken into consideration for antiarrhythmic treatment.

Hemodynamic effects of cibenzoline on normal myocardium and after pretreatment with DL-sotalol

The circulatory and myocardial effects of cibenzoline were investigated in 78 open-chest rats during and after a 7-min intravenous (i.v.) infusion. Measurements were performed in the intact circulation, and myocardial function was also examined by isovolumic registrations independent of circulatory changes. In the first part of the study, the dose-dependent effects of cibenzoline were investigated (2, 4, and 8 mg/kg vs. NaCl controls). Cibenzoline caused a dose-dependent decrease in heart rate (HR) (-16, -34, -37% vs. preinfusion values), mean aortic blood pressure (AoPm) (-8, -20, -30%), cardiac output (CO) (-6, -29, -39%), and dP/dtmax (+1, -21, -59%). The isovolumic peak left ventricular systolic BP (LVSBP) (-6, -6, -17%) and peak dP/dtmax (-8, -18, -54%) were also reduced. In the second part of the study, we examined the effects of 2 mg cibenzoline/kg after pretreatment with 2 mg DL-sotalol/kg: HR was -22% AoPm was -12%, CO was -29%, dP/dtmax was -40%, isovolumic LV pressure (LVP) was -12%, and peak dP/dtmax was -41%. Cibenzoline caused dose-dependent bradycardia, which cannot be explained by beta-adrenoceptor blockade. The auxotonic and isovolumic measurements indicate that cibenzoline possesses a dose-dependent negative inotropic effect: 2 mg cibenzoline/kg caused only a slight decrease in myocardial performance, but this effect was aggravated after pretreatment with DL-sotalol. Cibenzoline also increased peripheral resistance. The observed combination of negative inotropism and vasoconstriction caused by cibenzoline should be taken into consideration especially in patients with reduced LV function. This is of particular importance if cibenzoline is combined with DL-sotalol.

Tolerance of myocardium of aged animals to repeated oxygen deficiency

Hemodynamic and metabolic effects of three times 4 min of oxygen deficiency were investigated in 18-month-old rats in comparison to 4-month-old Wistar rats. Left-ventricular isovolumic-pressure-generating capacity and dp/dtmax during isovolumic conditions and hemodynamic indices during intact circulation were determined in open-chest rats. Additionally, high-energy phosphates were measured at the end of the experiments after 20 min of postasphyxial recovery. Older rats had a significantly reduced isovolumic left-ventricular pressure generating capacity (236 +/- 9 vs 269 +/- 5 mm Hg; p less than 0.05) and a low cardiac index (55 +/- 9 vs 117 +/- 8 ml x min-1 x kg-1). The effects of the oxygen deficiency were comparable in both groups. The isovolumic pressure generating capacity was reduced for 11% vs 14%, and dp/dtmax for 13% vs 13%. The myocardial ATP-content was also decreased for the same extent in both groups (0.6 vs 1.0 mumol/gww). Both hemodynamic and biochemical results indicate that aged myocardium does not have a reduced tolerance to repeated periods of oxygen deficiency.

Hemodynamic effects of the D- and L-isomers of sotalol on normal myocardium

This study investigated the hemodynamic effects of the D-isomer of sotalol in open-chest rats and compared this to the action of the L-isomer and the racemic DL-sotalol. Hemodynamic and additional isovolumic maximum measurements were registered at the end and 5 minutes after an intravenous infusion period of 7 minutes. DL- (1 and 2 mg/kg) and L-sotalol (2 mg/kg) caused a significant reduction in the heart rate and in the indices of contractility during and after infusion. D-sotalol (2, 4, and 8 mg/kg), however, decreased the contractility only transiently after very high doses at high plasma concentrations. Thus, while the effects of the beta-blocking L-isomer were comparable to those of DL-sotalol, only a slight and transient hemodynamic action of comparable doses of D-sotalol was found. These findings may be of significance for the proposed use of the D-isomer as a class-III antiarrhythmic agent.

Intraoperative valvuloplasty in calcific aortic stenosis: a study comparing the mechanism of a novel expandable device with conventional balloon dilatation

In selected patients with calcific aortic stenosis, balloon valvuloplasty is an intermediate alternative to surgery. The effect of balloon valvuloplasty to increase valve area, however, is limited and the restenosis rate is high during follow-up. To improve the results and reduce the complication rate, a new device for valvuloplasty of calcific aortic stenosis was developed. This system consists of three expandable prongs mounted on a freely movable catheter tip. To evaluate the efficacy of this new device, valvuloplasty was performed in 10 patients with severe aortic stenosis intraoperatively just prior to valve replacement. Comparison was made with the results of conventional balloon dilatation performed in an additional 20 patients during surgery. Using the new device, the relative orifice area increased from 10 +/- 3% before to 20 +/- 6% following intervention. However, in only one patient was a considerable increase of static valve area (greater than 15%) found. The results were comparable to the effect of conventional balloon dilatation, which led to an increase of orifice area from 12 +/- 7% to 24 +/- 10%. With both systems, the best results were achieved in patients with aortic stenosis and significant commissural fusion. In contrast, in bicuspid or tricuspid valves without fused commissures the effect of the intervention was limited. Because complete obstruction of the aortic valve does not occur during dilatation, this new device might be superior to conventional balloon dilatation. Preselection of patients according to the morphology of the valve seems mandatory to improve the success and reduce the complication rate of valvuloplasty in aortic stenosis.

Effects of the new class-III antiarrhythmic drug D-sotalol on contractile function of postischemic myocardium

The hemodynamic effects of the new class-III antiarrhythmic drug D-sotalol (2 mg/kg i.v.) on postischemic myocardium were investigated in comparison with the actions of the racemic D,L-sotalol (2 mg/kg i.v.) in rats. Drug infusion (7 min) was started 20 min after 3 x 4 min of global ischemic injury (oxygen deficiency). The left ventricular isovolumic pressure-generating capacity at the beginning of infusion was reduced by 15%, indicating postischemic dysfunction. Infusion of D-sotalol caused a highly significant (p less than 0.01) reduction of the left ventricular pressure-generating capacity (to 58 +/- 5%), as well as of the dp/dtmax (to 21 +/- 3%). Stroke volume (to 66 +/- 6%), ejection fraction (to 62 +/- 7%), and cardiac output (to 51 +/- 6%) were also decreased (p less than 0.01). Fifteen minutes after infusion a partial renormalization of the hemodynamic measures (dp/dtmax 41 +/- 5%; stroke volume 94 +/- 8%) was observed. Infusion of the racemic D,L-sotalol caused similar hemodynamic changes (left ventricular pressure-generating capacity 60 +/- 2%, dp/dtmax 25 +/- 2%), indicating its cardiodepressant action. In contrast to prior findings on normal myocardium, our present results indicate that D-sotalol, a potential new class-III antiarrhythmic drug, has a considerable negative inotropic effect on postischemic myocardium.

[Hemodynamic effects of disopyramide on postischemic and normal myocardium]

The acute effects of i.v. disopyramide (1.5 mg/kg) on the hemodynamics of postischemic hearts were investigated in comparison to normal ventricles. Infusion (7 min) was started in rats 20 min after 3 x 4 min of global ischemia during the period of stable postischemic dysfunction. 15 minutes after disopyramide i.v. (vs. NaCl control data) the cardiac output was reduced to 82 +/- 4% (vs. 101 +/- 5%; p less than 0.01) and dp/dtmax to 77 +/- 5% (vs. 83 +/- 3%). The maximum isovolumic pressure generating capacity as load-independent index of myocardial contractility was reduced to 89 +/- 2% (vs. 95 +/- 2%; p less than 0.05). In contrast to the results on postischemic myocardium no measureable change of the hemodynamics was detectable after the identical dose in normal animals without left ventricular dysfunction. Our results indicate an increased sensitivity of postischemic myocardium with modestly reduced contractile function to the hemodynamic effects of disopyramide, especially to the negative-inotropic effects.

[Negative inotropic effect of flecainide on the post-ischemic heart with limited contractile function]

The hemodynamic effects of 7 min i.v. flecainide were examined in rats with postischemic left ventricular dysfunction. For quantification of contractile function the isovolumic left ventricular pressure generating capacity and dp/dtmax were determined. Fifteen min after infusion the isovolumic maximum pressure was reduced for 33 mm Hg after flecainide (2 mg/kg; n = 12), whereas in the controls only a minimal reduction (12 mm Hg; n = 13) was found; dp/dtmax was also significantly reduced after flecainide. The results indicate - in contrast to prior investigations on normal hearts - a considerable negative action of 2 mg/kg flecainide i.v. on postischemic myocardium with reduced contractile function.