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J Soler-Soler

Publications and source records attributed to J Soler-Soler.

At least 73 records · Page 4Linked to original sources
PubMed1998

Relevance of delayed hospital admission on development of cardiac rupture during acute myocardial infarction: study in 225 patients with free wall, septal or papillary muscle rupture.

OBJECTIVES: We analyzed the possible relation between the presence of a hospital admission delay (> or =24 h), undue physical effort or recurrence of anginal pain, alone or in combination, with the development of free wall rupture (FWR), septal rupture (SR) or papillary muscle rupture (PMR) in patients with an acute myocardial infarction (AMI). BACKGROUND: Physical activity as a trigger of FWR in AMI remains controversial, and its contribution to SR or PMR remains unknown. Moreover, the role of ischemia or reinfarction as an additional cause of rupture has not been explored. METHODS: The incidence of hospital admission delay > or =24 h with maintenance of some ambulatory activity and the incidence of postinfarction angina were analyzed in consecutive patients with a first AMI with (n = 225) or without rupture (n = 1,012 [control group]) over different time periods. RESULTS: An admission delay > or =24 h occurred in 27 (27.6%) of 98 patients with FWR, 47 (47.0%) of 100 with SR and 14 (51.9%) of 27 with PMR but in only 81 (8%) of 1,012 control patients (p < 0.0001). Information on undue in-hospital effort preceding rupture was available for 111 patients and was present in 17 (32.7%) of 52 with FWR, 9 (18.4%) of 49 with SR and 3 (30%) of 10 with PMR versus only 76 (7.5%) of 1,012 control patients (p < 0.001). Information on postinfarction anginal pain was available for 114 patients with rupture and occurred in 30 (56.6%) of 53 with FWR, 30 (60%) of 50 with SR and 4 (36.4%) of 11 with PMR versus 120 (11.9%) of 1,012 control patients (p < 0.0001). Mean age and incidence of male gender, hypertension, absence of heart failure, single-vessel disease or occlusion of the infarct-related artery were comparable among the groups with FWR, SR or PMR. CONCLUSIONS: Delayed hospital admission or undue in-hospital physical activity appears to increase the risk of rupture in patients prone to this complication (i.e., a first transmural AMI, absence of overt heart failure and advanced age); recurrence of ischemia/infarction emerges as a potential additional trigger in a proportion of these patients.

Age Factors↗
PubMed1998

Regional expansion during myocardial ischemia predicts ventricular fibrillation and coronary reocclusion.

Primary ventricular fibrillation (VF) complicating acute myocardial infarction is associated with occluded infarction-related arteries. The relationship between VF during ischemia and spontaneous coronary reocclusion was analyzed in 48 anesthetized pigs submitted to 48 min of coronary ligation and 6 h of reflow. Reocclusion was associated with ischemic VF (6 of 11 animals with VF but only 6 of 37 without it had reocclusion) but not with reperfusion arrhythmias, the size of the ischemic area, the magnitude of electrocardiogram changes or contractile dysfunction during ischemia, or the severity of intimal injury at the occlusion site. The increase in end-diastolic length in the ischemic region during coronary occlusion was associated with ischemic VF (15 min after occlusion, end-diastolic length was 116 +/- 2 and 111 +/- 1% of baseline in animals with or without presenting subsequent VF, respectively) and was retained by multiple logistic regression analysis as the only independent predictor of ischemic VF and reocclusion. Thus ischemic VF is strongly associated with an increased rate of spontaneous coronary reocclusion during subsequent reperfusion. Acute expansion of ischemic myocardium appears as a prominent determinant of both ischemic VF and reocclusion.

Animals↗
PubMed1998

[Quantification of left-to-right shunt in atrial septal defect using oximetry, isotopes, and Doppler echocardiography. Is there a method of reference?].

INTRODUCTION: Determination of pulmonary to systemic blood flow ratio (QP/QS) is considered to be important for the management of patients with atrial septal defect. The QP/QS provides information on shunt severity and is usually determined by three methods: oximetry, first-pass radionuclide angiocardiography and Doppler echocardiography. The aim of the present study was to assess the accuracy and concordance level of these three methods in QP/QS quantification in atrial septal defects. PATIENTS AND METHODS: Sixty-four adult atrial septal defects patients in whom QP/QS was determined by these three methods with a 6 month interval were studied. Nuclear and echocardiographic post-surgical studies were repeated in 36 patients. RESULTS: QP/QS values determined by the three techniques had a low correlation between them: oximetry (r = 0.52; SEE = 0.74); radionuclide angiocardiography (r = 0.40; SEE = 0.79) and Doppler echocardiography (r = 0.72; SEE = 0.57). Radionuclide angiocardiography underestimated QP/QS > 3 (-0.61 +/- 1.21; p < 0.01). Only in 33% of studies there concordance (differences < 0.5) among the three methods and in 58% between two methods. Right ventricular dilatation and tricuspid regurgitation influenced radionuclide accuracy. Nevertheless, the correlation between this technique and echocardiography was satisfactory when the 36 post-surgical were included (r = 0.75); both techniques agreed in the diagnosis of the two cases with residual post-surgical shunt. CONCLUSIONS: Inter-method disparity in QP/QS quantification is high and no method can be used as a gold standard; clinical decisions therefore based on QP/QS quantification by one technique alone are ill-advised.

Adult↗
PubMed1998

Diagnostic accuracy of technetium-99m-MIBI myocardial SPECT in women and men.

UNLABELLED: Noninvasive diagnosis of coronary artery disease in women has some limitations due to a higher percentage of false-positive results. In addition, a lower prevalence of disease can be observed in this population. In this study, we evaluated the diagnostic accuracy of 99mTc-methoxy-isobutyl-isonitrile (MIBI) SPECT in women and men, in a group of patients with proven coronary artery disease by coronary angiography (select minority) and in all patients where a noninvasive test (silent majority) was performed. METHODS: Seven hundred and two consecutive patients without previous myocardial infarction were studied with 99mTc-MIBI myocardial SPECT. One hundred sixty-three patients had coronary angiography (select minority) and 539 did not (silent majority). All patients underwent exercise stress testing, and simultaneous dipyridamole was administered in 32% of patients who did not achieve maximum predicted heart rates. Diagnostic accuracy of the test was calculated for the select minority. Then, sensitivity and specificity of the silent majority were recalculated according to the Diamond criteria. RESULTS: Prevalence of coronary artery disease (32% versus 80%, p = 0.0001) and peak O2 consumption achieved in exercise tests (watts, exercise duration) were lower in women. The probability of positive results of 99mTc-MIBI SPECT also was lower in women (34% versus 65%). The sensitivity of 99mTc-MIBI SPECT in women of the select minority was lower (85% versus 93%, p = 0.01), whereas there was no significant difference for specificity (91% versus 89%). After correcting the results for the silent majority, there were no significant differences in sensitivity (87% versus 88%) and specificity (91% versus 96%) between women and men. These results were not different for patients who achieved maximum predicted heart rates during stress testing (without dipyridamole administration). CONCLUSION: The sensitivity of 99mTc-MIBI myocardial SPECT in women was lower than in men when only the select minority was considered. When the silent majority was considered (correction of selection bias) sensitivity and specificity results did not differ significantly between the sexes.

Cardiac Catheterization↗
PubMed1998

[Prosthetic valve endocarditis].

Infective endocarditis occurs in 4% of prosthetic valve carriers. The infection is related to both the injured endocardium and circulating microorganisms. Early prosthetic endocarditis, occurring in the first 12 months after valvular surgery is mainly caused by staphylococci, and late prosthetic endocarditis has a similar etiology as native valve endocarditis. Clinical manifestations of early cases are due to both bacteremia and prosthetic malfunction. In late cases the clinical picture is similar to native valve disease. Mortality in prosthetic endocarditis remains high, especially in early cases, despite combined medical and surgical treatment.

Echocardiography↗
PubMed1998

Should we still prescribe digoxin in mild-to-moderate heart failure? Is quality of life the issue rather than quantity?

The recently reported Digitalis Investigation Group (DIG) study has shown that digoxin has no demonstrable effect on survival in heart failure, but may be useful to ameliorate morbidity. The question may be raised whether digoxin is useful for symptomatic improvement in patients with mild or moderate heart failure. A major difficulty in answering this question is the lack of appropriate clinical measures of heart failure that allow a categorization such as mild, moderate and severe heart failure. However, data in several clinical trials permit an approach to this issue in an approximate way. For instance, the DIG study itself indicated that the beneficial clinical effect of digoxin was also apparent in pre-defined subgroups which corresponded to less severe forms of heart failure. The problem with the DIG study in this respect was the lack of direct measures of clinical improvement and the use of what might be taken as surrogates for these; however, it can probably be assumed that digoxin had a beneficial symptomatic effect even in patients with milder forms of heart failure. Direct clinical measures of clinical result were used in the Randomized Assessment of the effect of Digoxin on Inhibitors of ACE Study and the Prospective Randomized Study on Ventricular Failure and the Efficacy of Digoxin. Some inconsistencies between the clinical results of these trials may be explained partly on the basis of sample size, although on the whole the results point to a definite clinical improvement of patients on digoxin therapy, even when heart failure was considered to be mild on the basis of several measurements. Admittedly, the size of the effect of digoxin therapy in these patients may be quite modest. Although some concerns over safety may remain after the DIG trial, it can generally be accepted that digoxin is an effective drug for symptomatic improvement in patients with mild or moderate heart failure. The small size of this effect, however, indicates that the decision to use the drug may well be left to the discretion of the attending physician.

Clinical Trials as Topic↗
PubMed1997

Gap junction uncoupler heptanol prevents cell-to-cell progression of hypercontracture and limits necrosis during myocardial reperfusion.

BACKGROUND: The objective of this study was to test the hypothesis that chemical interaction through gap junctions may result in cell-to-cell progression of hypercontracture and that this phenomenon contributes to the final extent of reperfused infarcts. METHODS AND RESULTS: Cell-to-cell transmission of hypercontracture was studied in pairs of freshly isolated adult rat cardiomyocytes. Hypercontracture induced by microinjection of a solution containing 1 mmol/L Ca2+ and 2% lucifer yellow (LY) was transmitted to the adjacent cell (11 of 11 pairs), and the gap junction uncoupler heptanol (2 mmol/L) prevented transmission in 6 of 8 pairs (P=.003), with a perfect association between passage of the LY and transmission of hypercontracture. In the isolated, perfused rat heart submitted to 30 minutes of hypoxia, addition of heptanol to the perfusion media during the first 15 minutes of reoxygenation had a dose-related protective effect against the oxygen paradox, as demonstrated by a reduction of diastolic pressure and marked recovery of developed pressure (P<.001), as well as less lactate dehydrogenase release during reoxygenation (P<.001) and less contraction band necrosis (P<.001) than controls. In the in situ pig heart submitted to 48 minutes of coronary occlusion, the intracoronary infusion of heptanol during the first 15 minutes of reperfusion at a final concentration of 1 mmol/L limited myocardial shrinkage, reflecting hypercontracture (P<.05), reduced infarct size after 5 hours of reperfusion by 54% (P=.04), and modified infarct geometry with a characteristic fragmentation of the area of necrosis. Heptanol at 1 mmol/L had no significant effect on contractility of nonischemic myocardium. CONCLUSIONS: These results demonstrate that hypercontracture may be transmitted to adjacent myocytes through gap junctions and that heptanol may interfere with this transmission and reduce the final extent of myocardial necrosis during reoxygenation or reperfusion. These findings are consistent with the hypothesis tested and open a new approach to limitation of infarct size by pharmacological control of gap junction conductance.

Animals↗
PubMed1997

Changes in myocardial electrical impedance induced by coronary artery occlusion in pigs with and without preconditioning: correlation with local ST-segment potential and ventricular arrhythmias.

BACKGROUND: Myocardial ischemia increases tissue electrical resistivity leading to cell-to-cell uncoupling, and this effect is delayed by ischemic preconditioning in isolated myocardium. Alterations in myocardial resistivity elicited by ischemia in vivo may influence arrhythmogenesis and local ST-segment changes, but this is not well known. METHODS AND RESULTS: Myocardial impedance (resistivity [omega x cm] and phase angle [degrees]), epicardial ST segment, and ventricular arrhythmias were analyzed during 4 hours of coronary artery occlusion in 11 anesthetized open-chest pigs; these were compared with 13 other pigs submitted to a similar coronary occlusion preceded by ischemic preconditioning. Myocardial resistivity rose slowly during the first 34+/-7 minutes of occlusion (237+/-41 to 359+/-59 omega x cm), increased rapidly to 488+/-100 omega x cm at 60 minutes, and reached a plateau value (718+/-266 omega x cm, ANOVA; P<.01) at 150+/-69 minutes. By contrast, phase-angle changes began after 17 minutes of ischemia (-3.0+/-1.6 degrees to -4.2+/-1.2 degrees at 29+/-8 minutes) and evolved faster thereafter (-12.5+/-5.3 degrees at 144+/-56 minutes). Marked changes in myocardial impedance were observed during the reversion of ST-segment elevation that occurred 1 to 4 hours after occlusion, but impedance changes were less apparent during the early ST-segment recovery seen at 15 to 35 minutes of ischemia. The second arrhythmia peak (30+/-5 minutes) coincided with the fast change in tissue impedance, and both were delayed (P<.05) by ischemic preconditioning. CONCLUSIONS: A rapid impairment of myocardial impedance occurs after 30 minutes of coronary occlusion, and its onset is better defined by shift in phase angle than by rise in tissue resistivity. Phase 1b arrhythmias are associated with marked impedance changes, and both are delayed by preconditioning. Reversion of ST-segment elevation is partially associated with impairment of myocardial impedance, but other factors play a role as well.

Animals↗
PubMed1997

[Influence of ergometric parameters on the results of myocardial perfusion tomographic scintigraphy].

BACKGROUND: The percentage of peak predicted heart rate that is accepted to consider as sufficient a given exercise test is 85%. However, the optimal value of such rate and other exercise parameters for the purposes of myocardial single-photon emission tomography is not well established. PATIENTS AND METHODS: With the aim of establishing the minimal levels of maximal heart rate, product heart rate x systolic blood pressure and ventilatory oxygen uptake to obtain an adequate diagnostic efficacy of myocardial perfusion scintigraphy, 159 patients with coronary artery disease or suspicion of this without previous myocardial infarction were studied with stress test single photon emission tomography with 99mTc-methoxi-isobutil-isonitrile. All the patients were coronary angiography tested. RESULTS: Sensitivity and negative predictive value were significantly higher at levels of heart rate > 80% (93 vs 78%; p = 0.002 and 94 vs 56%; p = 0.0004), product heart rate x systolic blood pressure > 18,000 (88 vs 78%; p = 0.04 and 84 vs 52%; p = 0.004) and > 5 METs (85 vs 77%; p = 0.002 and 74 vs 69%; p = 0.03). CONCLUSIONS: Sensitivity and negative predictive value of stress test single photon emission tomography with 99mTc-methoxi-isobutil-isonitrile are low if levels higher than 80% of heart rate, 18,000 of product of heart rate x systolic blood pressure and 5 METs have not been achieved.

Aged↗
PubMed1997

Comparison of patients with and without papillary muscle rupture during acute myocardial infarction.

Seventeen of 31 patients with papillary muscle rupture (PMR) were admitted with a >24-hour delay since onset of acute myocardial infarction (AMI) in contrast to 81 of 1,012 with AMI without cardiac rupture; in 8 of 11 patients with in-hospital PMR it was preceded by new anginal pain in 5 and/or by strenuous exercise in 4; mortality was higher in those with anterior PMR, previous infarction, or 3-vessel disease than in those without PMR. Thus, persistence of physical activity before or during hospitalization, as well as postinfarction ischemia/infarct extension, appear to be relevant triggers of PMR, whereas mortality is more often associated with existence of a previous infarction, 3-vessel disease, and/or anterior PMR.

Aged↗
PubMed1997

Acute ischemic ventricular arrhythmias in pigs with healed myocardial infarction: comparative effects of ischemia at a distance and ischemia at the infarct zone.

BACKGROUND: The myocardium bordering a healed infarction undergoes electrophysiological and autonomic neural derangements that may interact with a new ischemic episode to promote arrhythmias. Therefore, peri-infarction ischemia may be more arrhythmogenic than ischemia at a distance from the infarct zone, but this is not known. METHODS AND RESULTS: Forty-two anesthetized open-chest pigs with a 1-month-old myocardial infarction induced by permanent ligature of the distal left anterior descending coronary artery (LAD) underwent a coronary reocclusion at either the proximal LAD (group 1, peri-infarction ischemia, n=21) or at the circumflex coronary artery (group 2, ischemia at a distance, n=21). Ventricular arrhythmias were analyzed during 60 minutes of coronary reocclusion and during programmed electrical stimulation. Infarct size was measured, and underperfusion at the occluded area was estimated by recording 99mTc-tetrofosmin activity. Weights of acute ischemic (23+/-9 versus 21+/-9 g) and healed infarction (10+/-6 versus 10+/-3 g), baseline LV pressure and peak of LV dP/dt, and radiotracer activity at the occluded area (3+/-2% versus 5+/-2% of normal tissue) were comparable between the two groups. Compared with group 2, group 1 showed more ventricular premature beats (median, 136 versus 59; P=.008), a higher incidence of spontaneous sustained ventricular tachycardia (57% versus 19%, P=.02) and ventricular fibrillation (76% versus 47%, P=.05), and greater electrical inducibility of sustained ventricular tachycardia (65% versus 28%, P=.03) but comparable induction of ventricular fibrillation. CONCLUSIONS: Ischemia superimposed at the border of a 1-month-old myocardial infarction is more arrhythmogenic than ischemia at a distance from the infarct zone in swine. Data suggest the presence of electrophysiological instability at the peri-infarction zone.

Animals↗
PubMed1997

Medical management of selected patients with left ventricular free wall rupture during acute myocardial infarction.

OBJECTIVES: This study sought to evaluate the effects of prolonged rest and blood pressure control on survival of patients in whom left ventricular free wall rupture (LVFWR) was strongly suspected. BACKGROUND: Left ventricular free wall rupture in myocardial infarction is often fatal, and only a few patients may undergo operation. However, survival without surgical repair has not yet been evaluated. METHODS: Eighty-one consecutive patients with a first transmural acute myocardial infarction in Killip class I or II who presented with acute hypotension due to cardiac tamponade, with electromechanical dissociation (EMD) in 72, were prospectively evaluated. Patients with early recovery were managed with prolonged bed rest and blood pressure control with beta-blockade as tolerated. RESULTS: Forty-seven patients died within 2 h of acute tamponade, and autopsy in 21 showed LVFWR in all. In 15 others, an emergency surgical repair resulted in 2 survivors. The remaining 19 patients, 10 with EMD, had early recovery with dobutamine and colloid solution, and 15 required pericardiocentesis. Shortly thereafter, these 19 patients still showed a paradoxic pulse > or = 20 mm Hg, relevant pericardial effusion (24 +/- 7 mm [mean +/- SD]) and comparable elevation of right and left ventricular filling pressures (15.8 +/- 3.9 and 15.9 +/- 3.8 mm Hg, respectively). Subsequent management included bed rest (8.2 +/- 4.8 days) and control of systolic blood pressure (< or = 120 mm Hg) with beta-adrenergic blocking agents as tolerated (n = 12). Four patients died, and autopsy in three revealed a rupture that was sealed in two. A sealed rupture was also seen at thoracotomy in 2 other patients who, like the remaining 13, survived for 52.5 +/- 35.2 months. CONCLUSIONS: Long-term survival of selected patients with prompt hemodynamic recovery after LVFWR is possible without surgical repair. Prolonged bed rest and blood pressure control are likely to contribute favorably to their initial outcome.

Adrenergic beta-Antagonists↗
PubMed1997

Simultaneous dipyridamole/maximal subjective exercise with 99mTc-MIBI SPECT: improved diagnostic yield in coronary artery disease.

OBJECTIVES: We attempted to demonstrate that simultaneous dipyridamole administration and maximal subjective exercise in patients who are unable to achieve a good exercise level can improve the diagnostic efficacy of technetium-99m methoxy isobutyl isonitrile (99mTc-MIBI) myocardial single-photon emission computed tomography (SPECT). BACKGROUND: The results of myocardial perfusion scintigraphy are unsatisfactory if the level of exercise achieved by the patient is insufficient. The use of dipyridamole with maximal subjective stress testing has been shown to improve the quality of the thallium-201 myocardial perfusion images, but there are no studies demonstrating that this combination improves the diagnostic accuracy of myocardial perfusion SPECT. METHODS: Two hundred thirty-one consecutive patients, without a previous myocardial infarction, were classified into three groups: group 1, 91 patients with an adequate exercise test; group 2, 68 patients with an inadequate exercise test; group 3, 72 patients with an inadequate exercise test who then received intravenous dipyridamole (0.56 mg/kg body weight over 4 min) simultaneously with exercise. RESULTS: Results for sensitivity (89%) and negative predictive value (83%) in group 3 were significantly better than those in group 2 (71% [p = 0.03] and 56% [p = 0.002], respectively) and not significantly different from those in group 1. The polar maps of 20 patients studied with an without dipyridamole at the same exercise level revealed a significantly greater extent of ischemia in each territory and in a global assessment (19 + 20% vs. 8 + 11%, p < 0.0001) when dipyridamole was administered during physical exercise. CONCLUSIONS: Intravenous dipyridamole administration during exercise testing is advisable in all patients who are unable to achieve an adequate exercise level. This approach permits physicians to avoid missing ergometric information while optimizing myocardial SPECT results.

Cardiac Catheterization↗
PubMed1997

Culprit lesion and jeopardized myocardium: correlation between coronary angiography and single-photon emission computed tomography.

BACKGROUND: The term "culprit lesion" is used to designate the coronary stenosis responsible for the symptoms of the patient with coronary artery disease. Its detection is essential when partial revascularization is contemplated. The term "jeopardized myocardium" is commonly used to mean the amount of myocardium put in danger by all the stenotic lesions; however, it should be restricted to the amount of myocardium that could become infarcted if only the most severe stenoses were occluded. HYPOTHESIS: The aim of this study was to investigate (1) the agreement between coronary myocardial single-photon emission computed tomography (SPECT) and coronary angiography for the identification of the culprit lesion, and (2) the correlation of the two studies in the quantification of jeopardized myocardium. METHODS: In all, 159 patients with coronary artery disease without previous myocardial infarction were included in the study. A score for myocardial SPECT was correlated with the angiographic scores by Califf and Gensini and with the authors' score which includes adjustment for collateral circulation. RESULTS: The agreement between coronary angiography and SPECT for the diagnosis of the culprit lesion was 84% (87/104). The correlations between the scores of angiography and SPECT to assess jeopardized myocardium when all coronary stenoses were taken into account were significant (p < 0.0001), but their coefficients were suboptimal (r = 0.48 for Califf, r = 0.48 for Gensini, and r = 0.65 for the authors' score). When only the jeopardized myocardium resulting from the culprit lesion was considered, the correlation clearly improved (r = 0.85). CONCLUSION: Thus, in 84% of patients with multivessel disease, an agreement between coronary angiography and myocardial SPECT for the diagnosis of the culprit lesion was observed. The correlation between these techniques for the quantification of jeopardized myocardium from the culprit lesion was satisfactory.

Cardiac Catheterization↗
PubMed1997

A randomized controlled trial of epoprostenol therapy for severe congestive heart failure: The Flolan International Randomized Survival Trial (FIRST).

This trial evaluated the effects of epoprostenol on patients with severe left ventricular failure. Patients with class IIIB/IV congestive heart failure and decreased left ventricular ejection fraction were eligible for enrollment if angiography documented severely compromised hemodynamics while the patient was receiving a regimen of digoxin, diuretics, and an angiotensin-converting enzyme inhibitor. We randomly assigned 471 patients to epoprostenol infusion or standard care. The primary end point was survival; secondary end points were clinical events, congestive heart failure symptoms, distance walked in 6 minutes, and quality-of-life measures. The median dose of epoprostenol was 4.0 ng/kg/min, resulting in a significant increase in cardiac index (1.81 to 2.61 L/min/m2), a decrease in pulmonary capillary wedge pressure (24.5 to 20.0 mm Hg), and a decrease in systemic vascular resistance (20.76 to 12.33 units). The trial was terminated early because of a strong trend toward decreased survival in the patients treated with epoprostenol. Chronic intravenous epoprostenol therapy is not associated with improvement in distance walked, quality of life, or morbid events and is associated with an increased risk of death.

Aged↗
PubMed1997

Lack of evidence of M-cells in porcine left ventricular myocardium.

OBJECTIVE: The aim of this study was to analyze whether cells with long action potential duration, fast Vmax, and spike-and-dome configuration (M-cells) are present in porcine left ventricular myocardium. METHODS: Transmembrane action potentials (n = 505) of the left ventricle were recorded with conventional glass microelectrodes in an epicardial-endocardial direction at 2000 ms basic cycle length in 14 pigs. In 3 pigs, potentials were obtained at 1000, 2000, and 5000 ms cycle length before and after superfusion with quinidine HCl 1 microgram/ml. In addition, transmembrane potentials (n = 52) were recorded in 4 dogs at 2000 ms cycle length to verify the ability of our protocol to detect M-cells. RESULTS: In pigs, action potential duration at 90% repolarization was shorter (ANOVA, P < 0.001) and Vmax slower (P < 0.001) in the epicardium than in the other transmural sites, but there were no regional differences in resting membrane potential or in action potential amplitude. Potentials with particularly long phase 3 or with spike-and-dome configuration were not observed. All myocardial sites displayed rate dependence of action potential duration (P = 0.02) which was transmurally homogeneous and persisted after quinidine exposure. The drug did not induce afterdepolarizations. In dogs, potentials with spike-and-dome configuration, long duration, and fast Vmax, like those described in M-cells, were detected in deep epicardial and midmyocardial areas. CONCLUSION: The porcine left ventricular myocardium shows transmural differences in action potential duration and Vmax, but, unlike dogs, it lacks M-cells.

Action Potentials↗
PubMed1997

Prevention of ischemic rigor contracture during coronary occlusion by inhibition of Na(+)-H+ exchange.

OBJECTIVE: To determine the effect of Na(+)-H+ exchange blockade on ischemic rigor contracture and reperfusion-induced hypercontracture. METHODS: Thirty-six pigs were submitted to 55 min of coronary occlusion and 5 h reperfusion. Myocardial segment length analysis with ultrasonic microcrystals was used to detect ischemic rigor (reduction in passive segment length change) and hypercontracture (reduction in end-diastolic length). RESULTS: Pretreatment with the new, highly selective Na(+)-H+ exchange inhibitor HOE642 before occlusion reduced ischemic rigor (P < 0.05), attenuated segment shrinkage (P < 0.05) during subsequent reperfusion, dramatically reduced infarct size (P < 0.0001) and attenuated arrhythmias (P < 0.01). Inhibition of Na(+)-H+ exchange only during reperfusion by means of direct intracoronary infusion of HOE642 into the area at risk prevented reperfusion arrhythmias but had no effect on final infarct size, while treatment with intravenous HOE642 immediately before reperfusion had no detectable effects. CONCLUSION: These results indicate that inhibition of Na(+)-H+ exchange during ischemia is necessary to limit myocardial necrosis secondary to transient coronary occlusion, and that this action could by mediated by a protective effect against ischemic contracture. Inhibition of Na(+)-H+ exchange only during reperfusion has a partial and transient beneficial effect, but only when the inhibitor reaches the area at risk before reflow.

Animals↗