Effects of nitroglycerin on left ventricular volumes and wall tension in patients with ischaemic heart disease

Method comparison for cardiac image registration of coronary computed tomography angiography and 3-D echocardiography

Treatment decision for coronary artery disease (CAD) is based on both morphological and functional information. Image fusion of coronary computed tomography angiography (CCTA) and three-dimensional echocardiography (3DE) could combine morphology and function into a single image to facilitate diagnosis. Three semiautomatic feature-based methods for CCTA/3DE registration were implemented and applied on CAD patients. Methods were verified and compared using landmarks manually identified by a cardiologist. All methods were found feasible for CCTA/3DE fusion.

Coronary collaterals during single-vessel coronary angioplasty: effects of nitroglycerin

BACKGROUND

Although the protective role of collaterals in coronary artery disease (CAD) is well known, the influence of drugs on collateral function remains controversial.

HYPOTHESIS

We aimed to investigate prospectively the prevalence of spontaneously visible and recruitable coronary collaterals in consecutive patients with single-vessel CAD and the effect of systemic administration of nitroglycerin on these types of collaterals during percutaneous transluminal coronary angioplasty (PTCA).

METHODS

Ipsi- and contralateral coronary artery contrast injections were performed before and during PTCA. Simultaneously with balloon occlusion, we measured coronary artery occlusion pressure via the balloon catheter. All measurements were repeated after administration of 0.5 mg of nitroglycerin intravenously.

RESULTS

Of 101 consecutive patients, 24% had spontaneously visible and 30% had recruitable collaterals. Contralateral collaterals were five times more frequent than ipsilateral collaterals. Presence of collaterals was highly associated with the degree of coronary stenosis. Coronary occlusion pressure was higher in patients with than in those without collaterals. Collaterals prevented pain and ischemia during PTCA, and in this respect spontaneously visible collaterals were more effective than recruitable collaterals. There was no effect of systemic administration of nitroglycerin on appearance or occlusion pressure of coronary collaterals.

CONCLUSION

Coronary collaterals were found in more than half of patients with single-vessel CAD, as the prevalence of recruitable collaterals was slightly higher than that of spontaneously visible collaterals. Nitroglycerin did neither recruit nor augment coronary collaterals.

Underestimation of extent and severity of coronary artery disease by dipyridamole stress thallium-201 single-photon emission computed tomographic myocardial perfusion imaging in patients taking antianginal drugs

OBJECTIVES

This study evaluated the diagnostic value of dipyridamole plus low level treadmill exercise (dipyridamole stress) thallium-201 single-photon emission computed tomography (SPECT) in patients taking antianginal drugs.

BACKGROUND

Dipyridamole stress is the major substitute for maximal exercise in patients referred for myocardial perfusion imaging. Although antianginal drugs are commonly suspended before exercise, dipyridamole stress is usually performed without discontinuing these drugs.

METHODS

Twenty-six patients underwent two dipyridamole perfusion studies: the first without (SPECT-1) and the second with (SPECT-2) antianginal treatment. Twenty-one patients (81%) received calcium antagonists, 19 (73%) received nitrates, and 8 (31%) received beta-blockers. Eighteen of the patients underwent coronary angiography. Data are presented as the mean value +/- SD.

RESULTS

Visual scoring yielded significantly larger and more severe reversible perfusion defects for SPECT-1 than for SPECT-2. Quantitative analysis showed larger perfusion defects on stress images of SPECT-1 in the left anterior descending coronary artery (LAD) (25 +/- 21% vs. 17 +/- 15%, p = 0.003), left circumflex coronary artery (LCx) (56 +/- 35% vs. 48 +/- 36%, p = 0.03) and right coronary artery (RCA) (36 +/- 27% vs. 25 +/- 24%, p = 0.008) territories. Individual vessel sensitivities in the LAD, LCx and RCA territories were 93%, 79% and 100% for SPECT-1 and 64%, 50% and 70% for SPECT-2, respectively. These differences were highly significant for the LAD (p = 0.004) and LCx (p = 0.00004) territories. The overall individual vessel sensitivity of SPECT-1 was significantly higher than that of SPECT-2 (92% vs. 62%, p = 0.000003). Specificity was not significantly different in SPECT-1 compared with SPECT-2 (80% and 93%, p = 0.33).

CONCLUSIONS

Continued use of antianginal drugs before dipyridamole plus low level treadmill exercise thallium-201 SPECT may reduce the extent and severity of myocardial perfusion defects, resulting in underestimation of coronary artery disease.

Effect of intracoronary nitroglycerin administration on phasic pattern and transmural distribution of flow during coronary artery stenosis

BACKGROUND

Nitroglycerin is effective in relieving myocardial ischemia; however, intracoronary nitroglycerin often fails to relieve angina and has been reported to have deleterious effects on subendocardial blood flow. To understand the mechanisms involved, we evaluated the direct effect of nitroglycerin on coronary circulation of the ischemic hearts.

METHODS AND RESULTS

We measured the phasic pattern of intramyocardial coronary arterial flow with an 80-channel, 20-MHz pulsed Doppler ultrasound flowmeter under moderate to severe coronary artery stenosis (distal perfusion pressure approximately 45 mm Hg group 1, n = 6) and transmyocardial blood flow distribution using radioactive microspheres while maintaining coronary pressure at a low constant level (40 mm Hg, group 2, n = 6). In anesthetized open-chest dogs, the left main coronary artery was perfused directly from the right carotid or femoral artery. In this bypass circuit, pressure was controlled with an occluder or a reservoir was connected to the circuit. In group 1, the systolic and diastolic pressures distal to the stenosis decreased significantly after intracoronary administration of nitroglycerin at maximal coronary flow from 66.5 +/- 18.5 to 56.5 +/- 13.8 mm Hg (p less than 0.01) and from 36.6 +/- 14.4 to 27.5 +/- 8.9 mm Hg (p less than 0.01), respectively. The phasic pattern of the septal artery flow was predominantly diastolic and was characterized by systolic reverse flow even in the absence of stenosis. Coronary stenosis increased systolic reverse flow. Nitroglycerin increased diastolic forward flow (p less than 0.05) but augmented systolic reverse flow markedly (p less than 0.001). In group 2, nitroglycerin increased subepicardial flow (p less than 0.05) but failed to increase subendocardial flow. With the administration of nitroglycerin, the subendocardial-to-subepicardial flow ratio decreased significantly from 0.73 +/- 0.19 to 0.32 +/- 0.14 (p less than 0.01).

CONCLUSIONS

The increased systolic reverse flow after intracoronary administration of nitroglycerin may be closely related to failure of subendocardial blood flow to increase with increase subepicardial flow.

Effects of nitroglycerin in patients with angina, normal coronary arteries, and left ventricular hypertrophy

The coronary hemodynamic and left ventricular mechanical responses to nitroglycerin were studied in eight patients with angina, normal coronary arteries, and pressure overload left ventricular hypertrophy (POLVH) and in five control subjects. Elevated mean and end-diastolic pressure and end-diastolic meridional stress characterized the POLVH group, although systolic meridional stresses were not significantly different from the control group. Thermodilution coronary sinus flow and estimated myocardial oxygen consumption declined significantly following nitroglycerin in both patient groups. Systolic and diastolic mechanical loads also decreased in both groups, although diastolic tone remained elevated in the patients with POLVH. The decrease in coronary sinus flow in the POLVH group was in excess of that expected from the decrease in systolic mechanical load, which suggests a combination of perfusion pressure-dependent decreases in coronary flow as well as an increased resistance to coronary inflow in these patients. The beneficial clinical response to nitroglycerin may reflect the lowered myocardial metabolic demand as well as the decrease in diastolic myocardial tensile and compressive forces.

Dynamics of mitral regurgitation during nitroglycerin therapy: a Doppler echocardiographic study

Seven patients with decompensated chronic heart failure and functional mitral regurgitation were studied before and during administration of nitroglycerin at a mean dose of 42 micrograms/min (range 20 to 90 micrograms/min). Forward aortic flow obtained by pulsed Doppler increased significantly from 35 +/- 8 to 45 +/- 9 ml/beat (p less than 0.001) and correlated well with the cardiac output measured by thermodilution technique (r = 0.8). Whereas regurgitant mitral volume calculated from the difference between echocardiographic total stroke volume and forward aortic flow decreased significantly from 19 +/- 9 to 3 +/- 3 ml/beat (p less than 0.001), peak velocity of mitral regurgitant flow increased from 4.1 +/- 0.9 to 4.4 +/- 1.0 m/sec (p less than 0.05). The decrease in effective mitral regurgitation area derived from a modified Gorlin formula average 80%. Accordingly, in patients with decompensated chronic heart failure and functional mitral regurgitation, nitroglycerin decreases mitral regurgitant area substantially, and thus almost abolishes mitral regurgitation despite an increase in systolic pressure gradient between left ventricle and atrium. Moreover, the increase in forward flow can be entirely accounted for by the reduction in mitral regurgitant flow.

Role of isosorbide dinitrate in patients with unstable angina pectoris

The development of hemodynamic facilities permitted observations after isosorbide dinitrate (ISDN) administration over a 4-hour period in patients with a history of unstable angina pectoris and documented anatomic coronary artery disease. The patients had no evidence of left ventricular failure and were free of pain during the period of sublingual and oral ISDN administration. Beneficial influences on venous return and arterial blood pressure were manifested as declines in preload and afterload, along with reduction in the mechanical work of the ventricle and, finally, increases in the diastolic compliance of the ventricle. These hemodynamic changes were shown to persist 8 to 12 times as long as the brief influence of nitroglycerin. Thus hemodynamic evidence was provided for the first time on the beneficial influence of oral and sublingual ISDN on venous, arterial, and left ventricular myocardial muscle in patients with unstable angina pectoris.

Myocardial exchange of metabolites after nitroglycerin in patients with coronary artery disease

We studied the effects of sublingual nitroglycerin (dose range 0.5-1.0 mg) on cardiac metabolism in the resting state in 12 patients with chronic coronary artery disease. Seven patients with chronic coronary artery disease served as a control group. No patient from either of the groups experienced angina pectoris during the study. Reduced heart work after nitroglycerin was evident from a 34% decrease of oxygen uptake (P less than 0.001) and a 35% fall in coronary sinus blood flow (P less than 0.01). Nitroglycerin decreased lactate extraction by 30% (P less than 0.05), lactate uptake by 58% (P less than 0.025); glucose uptake by 47% (P less than 0.01) while net exchange of free fatty acids did not change. The aorto-coronary sinus difference of plasma citrate became increasingly negative (from -4 +/- 3 mumol/l to -8 +/- 2 mumol/l) (P less than 0.02) after nitroglycerin. In the control group coronary sinus blood flow and myocardial exchange of oxygen and substrates remained unchanged. Our results suggest a relatively increased myocardial utilization of free fatty acids compared with that of carbohydrates after nitroglycerin. This may in part be explained as an inhibition of glycolysis due to citrate accumulation. The study indicates that myocardial lipid-carbohydrate metabolism is disturbed in chronic coronary artery disease even in patients without clinical evidence of ischaemia in resting state and that nitroglycerin reverses this condition towards the metabolism of the normal heart.

Hemodynamic effects of high-dose sustained-action oral isosorbide dinitrate in stable angina

Hemodynamic effects of sustained-action oral isosorbide dinitrate (40 or 80 mg) were studied in 10 patients with stable angina for a period of 16 hours. Control hemodynamic parameters monitored for eight hours prior to the administration of isosorbide dinitrate showed no significant change. However significant reduction in mean arterial pressure, cardiac index, pulmonary artery wedge pressure, mean pulmonary artery pressure, double product (systolic pressure multiplied by heart rate), stroke volume index, and stroke work index occurred in the first two hours and persisted for 12 hours following the administration of isosorbide dinitrate. Heart rate did not change significantly for 12 hours. It can be concluded that the hemodynamic effects of sustained-action oral isosorbide dinitrate occur in the first two hours and last up to 12 hours. The predominant hemodynamic effect appears to be on the myocardial preload. The antianginal effect of the drug could be attributed to the reduction of myocardial oxygen demand reflected by a decrease in the double product and stroke work. The duration of the hemodynamic changes observed in this study indicates that high-dose oral isosorbide dinitrate could be administered conveniently two or three times daily.

Increased coronary sinus lactate concentration during pacing induced angina pectoris after clinical improvement by glyceryl trinitrate

Ten patients with stable angina pectoris and obstructed coronary arteries (greater than 75% reduction in diameter) were studied before and during two periods of pacing, the second of which was preceded by sublingual administration of glyceryl trinitrate (mean dose 0.78 mg). Coronary sinus blood flow measurements and aortocoronary sinus blood sampling for metabolite determinations were carried out. Although the rate of pacing was increased by 10 beats/minute after glyceryl trinitrate administration, the onset of angina was delayed in eight patients during pacing. Drug administration decreased coronary sinus blood flow by 42% and myocardial oxygen uptake by 41% during pacing and induced a shift in mean lactate extraction towards a net release (from 3.1% to -12.6%). It increased the number of patients producing lactate from three to five. Glyceryl trinitrate administration decreased myocardial glucose uptake throughout the study, decreased lactate extraction during recovery, and increased the aortocoronary sinus citrate gradient at rest and during recovery, while the exchange of free fatty acids remained unchanged. A decrease in aortocoronary sinus lactate difference during pacing after glyceryl trinitrate administration correlated positively with the fall in coronary sinus blood flow. The metabolic data do not indicate an augmented myocardial lactate production after glyceryl trinitrate administration. A decrease in coronary sinus blood flow seems, therefore, to be of primary importance in explaining the elevated coronary sinus lactate concentration. Our finding that coronary sinus lactate concentration increased during pacing after glyceryl trinitrate administration despite clinical improvement questions the validity of its use as a quantitative index of ischaemia.

Effects of nitroglycerin and propranolol on the distribution of transmural myocardial blood flow during ischemia in the absence of hemodynamic changes in the unanesthetized dog

Chronically instrumented awake dogs were used to study the effects of nitroglycerin and propranolol on the transmural distribution of myocardial blood flow during transient ischemia. Studies were carried out 7-14 d after implantation of an electromagnetic flowmeter probe and balloon occluder on the left circumflex coronary artery, placement of epicardial minor axis sonar crystals, and implantation of left atrial, left ventricular, and aortic catheters. The occluder was inflated to completely interrupt flow for 10 s followed by partial release to reestablish flow at 60% of the preocclusion level. During this partial release, which served as the control for the study, regional myocardial blood flow was measured with 7- to 10-mum radioactive microspheres. After control measurements, seven dogs were given nitroglycerin (0.4 mg i.v.) and eight dogs propranolol (0.2 mg/kg i.v.). 5 min later the occlusion and partial release sequence was repeated, and regional myocardial blood flow was measured when heart rate, aortic and left ventricular end-diastolic pressure, and minor axis diameter were unchanged from control values.The data values were selected so that total flow to the ischemic region during partial release after nitroglycerin or propranolol administration was not significantly different from flow during the control partial release. After nitroglycerin administration, endocardial flow (endo) in the ischemic region increased from 0.46+/-0.07 to 0.59+/-0.06 ml/min per g (P < 0.006); epicardial flow (epi) decreased from 0.78+/-0.09 to 0.70+/-0.08 ml/min per g (P < 0.04). The endo:epi ratio increased from 0.65+/-0.07 to 0.92+/-0.10 (P < 0.05). In contrast, administration of propranolol produced no significant change in transmural flow (endo, 0.42+/-0.02 and 0.46+/-0.03 ml/min per g; epi, 0.71+/-0.06 and 0.70+/-0.07 ml/min per g) or in the endo:epi ratio (0.60+/-0.03, 0.66+/-0.06) in the ischemic region. Nitroglycerin and propranolol produce different effects on the transmural distribution of blood flow to ischemic myocardium. Nitroglycerin can increase blood flow to the underperfused endocardium in the absence of alterations in heart size, hemodynamic parameters, and total transmural flow to the ischemic region. Under similar conditions, propranolol has no significant effect on the transmural distribution of blood flow to an ischemic region.

Afterload reduction and cardiac performance. Physiologic basis of systemic vasodilators as a new approach in treatment of congestive heart failure

Digitalis and diuretics constitute conventional therapy of congestive heart failure, but systemic vasodilators offer an innovative approach in acute and chronic heart failure of decreasing increased left ventricular systolic wall tension (ventricular afterload) by reducing aortic impedance and/or by reducing cardiac venous return. Thus, vasodilators increase cardiac output (CO) by diminishing peripheral vascular resistance (PVR) and/or decrease increased left ventricular end-diastolic pressure (LVEDP) (ventricular preload) by diminishing venous tone. Concomitantly, there is reduction of myocardial oxygen demand, thereby reliably reducing angina pectoris in coronary disease, and potentially limiting infarct size and ischemia provided systemic arterial pressure remains normal. The vasodilators produce disparate modifications of cardiac function depending upon their differing alterations of preload versus impedance: nitrates principally cause venodilation (decrease LVEDP); nitroprusside, phentolamine and prazosin produce balanced arterial and venous dilation (decrease LVEDP and increase CO) provided left ventricular filling pressure is maintained at the upper limit of normal; whereas hydralazine predominantly effects arteriolar dilation (increases CO). With depressed CO plus highly increased LVEDP and increased PVR, nitrates also induce some increase of CO by reducing PVR. Combined nitroprusside and dopamine synergistically enhance CO and decrease LVEDP. Mechanical counterpulsation aids nitroprusside in acute myocardial infarction. The 30-minute venodilator action of sublingual nitroglycerin is extended for 4 to 6 hours by cutaneous nitroglycerin ointment, by sublingual and oral isosorbide dintrate, and by oral pentaerythritol tetranitrate and sustained-release nitroglycerin capsules. Ambulatory oral vasodilator therapy is provided by long-acting nitrates (relieve pulmonary congestion); hydralazine (improves fatigue); prazosin alone, combined nitrate-hydralazine combined prazosin-hydralazine (improve both dyspnea and fatigue).

Comparative effects of glyceryl trinitrate on venous and arterial smooth muscle in vitro; relevance to antianginal activity

1. A quantitative in vitro study has been made of the actions of glyceryl trinitrate and sodium nitrite on vascular smooth muscle (dog femoral artery and saphenous vein; rat portal vein); these have been compared with the actions of papaverine, isoprenaline, salbutamol, pentaerythritol tetranitrate and trimetazidine. 2. Glyceryl trinitrate was more active on the saphenous vein than on the femoral artery in inhibiting noradrenaline and potassium-induced tone. 3. Unlike glyceryl trinitrate, sodium nitrite and isoprenaline, papaverine and diazoxide inhibited noradrenaline-induced contractions of venous and arterial smooth muscle to the same extent. 4. The selective dilator effects of glyceryl trinitrate on venous smooth muscle may explain its action in alleviating the pain of angina pectoris. It is suggested that the use of these three vascular smooth muscle preparations (arterial, and veins with and without spontaneous myogenic activity) is a useful initial screening procedure for prospective antianginal drugs acting by venodilatation.

Nitroglycerin and propranolol on myocardial O2 consumption during myocardial ischemia

The effects of i.v. and intracoronary (i.c.) nitroglycerin, i.v. propranolol, and the combination of propranolol and nitroglycerin on myocardial oxygen consumption (MVO2) and lactate utilization were studied in situ ischemic working dog hearts. I.v. nitroglycerin reduced MVO2 9% which was associated with the peripheral vasodilatory actions of the drug. I.c. nitroglycerin which had no detectable effects on the peripheral vasculature had no significant effect on MVO2. I.v. propranolol caused an 8% reduction in MVO2 and this action was associated with a negative chronotropic and a slight negative inotropic effect. However, the combination of propranolol and nitroglycerin which was more effective than either drug alone, reduced MVO2 18% thereby indicating that the effects of the two drugs on oxygen consumption are additive. These results support the concept that the reduction of MVO2 seen with nitroglycerin is principally due to peripheral vasodilatory actions of the drug while that seen with propranolol is due to that drug's effect on the heart and the effects of the two agents are complementary.

Nitroglycerin and ventricular performance. Differential effect in the presence of reversible and irreversible asynergy

The effect of nitroglycerin administration on left venticular performance relative to its ability to improve contraction of asynergic zones was examined in 66 patients with coronary artery disease, divided into those whose asynergic zones responded following nitroglycerin administration and those in whom no response was observed. In the responsive group with asynergy of more than one segment, the ejection fraction improved (P less than 0.001), while in the unresponsive group, it decreased (P less than 0.05). Similarly, in patients with one-segment asynergy, the responsive group exhibited a significant increase in ejection fraction P less than 0.001), while the unresponsive group showed no change. The stroke volume index remained unchanged in the responsive group with asynergy of more than one segment, while it decreased significantly (P less than 0.05) in the unresponsive patients. Left ventricular pressures and volumes changed to a similar degree after nitroglycerin administration in all of the patients, regardless of the responsiveness of asynergic zones. It is concluded that nitroglycerin administration results in a differential effect on total left ventricular performance depending on the responsiveness of asynergic zones.

Regional and global myocardial effects of intravenous and sublingual nitroglycerin treatment after experimental acute coronary occlusion

The consequences of sublingual and intravenous nitroglycerin treatment after acute coronary occlusion were studied in 18 closed chest dogs. Intravenous (0.1 mg/min) or sublingual (0.4 mg/15 min) nitroglycerin therapy was instituted 1 hour after occlusion and the effects were observed over a period of 2 hours. Hemodynamics and global and regional cardiac function were measured in both the coronary occluded and nonoccluded segments of the left ventricle before and during coronary occlusion, and after administration of nitroglycerin. A similar nine dog control series was used to establish the significance of the measured effects of nitroglycerin. Intravenous nitroglycerin therapy after 1 hour of occlusion resulted in a marked increase in heart rate (37 +/- 12 [mean +/- standard error of the mean] percent), reduction of systolic blood pressure (9 +/- 3%), decrease in left ventricular end-diastolic and end-systolic volumes (32 +/- 5% and 34 +/- 5%), increase in coronary sinus flow (64 +/- 24%) and decrease in left ventricular stroke work (29 +/- 8%). Sublingually administered nitroglycerin produced similar trends but much less pronounced effects. However, intravenous or sublingual administration of nitroglycerin provided no improvement or caused further deterioration in ischemic region lactate extraction and potassium loss. The left ventricular ejection fraction, which was severly depressed after 1 hour of occlusion, changed minimally after administration of nitroglycerin, and there was no evidence of any correction of regional left ventricular akinesia or dyskinesia. Whereas mean systemic vascular resistance changed minimally as a result of nitroglycerin therapy, it increased 19 +/- 8% during a corresponding period of an untreated coronary occlusion series suggesting that nitroglycerin prevented an anticipated increase. Postocclusion S-T segment elevation in the electrocardiogram persisted after treatment. Our data corroborated that nitroglycerin reduced left ventricular volumes and increased coronary sinus flow; however, these improvements were accompanied by persisting metabolic and mechanical derangements in the ischemic region.

Hemodynamic effects of isosorbide dinitrate vs nitroglycerin in patients with unstable angina

The hemodynamic response to nitroglycerin administration, to sublingual or oral administration of isosorbide dinitrate, or to a placebo was evaluated and compared in 37 patients with unstable angina pectoris under resting, pain-free conditions. Patients with congestive heart failure were not included in this study. Serial measurements of mean arterial blood pressure (MAP), pulmonary arterial end-diastolic pressure (PAEDP), cardiac index (CI), and heart rate (HR) were obtained for one hour following nitroglycerin administration and for four hours following sublingual or oral administration of isosorbide dinitrate. Echocardiographic end-diastolic volume (EDV) measurements were obtained for the groups receiving isosorbide dinitrate or placebo. There was a significant (P less than 0.05 or less than 0.1) reduction of the MAP (5 to 10 mm Hg) that persisted for more than four hours following both sublingual and oral administration of isosorbide dinitrate. The changes in the PAEDP, HR, and CI following sublingual or oral administration of isosorbide dinitrate were small and not significant. In the group receiving isosorbide dinitrate sublingually, the EDV was reduced by more than 30 ml below the placebo group (P less than 0.1) for up to four hours. The effects of nitroglycerin administration were similar in magnitude but of much shorter duration (three to four hours for sublingual and oral administration of isosorbide dinitrate vs 15 to 30 minutes for nitroglycerin). These data demonstrate that the duration of the hemodynamic effects of sublingually and orally administered isosorbide dinitrate in patients with unstable angina pectoris and normal resting hemodynamics is 8 to 12 times longer than that of nitroglycerin.

Effects of nitroglycerin on the major determinants of myocardial oxygen consumption. An angiographic and hemodynamic assessment

A direct and quantitative study of the effects of sublingually administered nitroglycerin on the major determinants of myocardial oxygen consumption was carried out in 10 patients, 7 with coronary artery disease. Left ventricular wall tension, estimates of the contractile state and heart rate were studied directly using simultaneous pressure measurements and angiographically obtained volume determinations. The peak systolic left ventricular wall tension decreased 15 percent after administration of nitroglycerin, suggesting a diminished myocardial oxygen requirement. Increased myocardial oxygen requirements were suggested by the occurrence of both positive chronotropic and inotropic effects. Heart rate increased 15 percent. The mean circumferential fiber shortening velocity increased 26 percent and the ejection fraction 30 percent; these findings, in association with a 23 percent reduction in left ventricular end-diastolic volume, were considered consistent with an increase in the contractile state. The mechanism of action of nitroglycerin seems to relate best to the decrease in systolic wall tension. The end-diastolic tension decreased 57 percent, suggesting the possibility that diastolic coronary blood flow may be augmented by diminished extravascular resistance to flow.

Reversibility of left ventricular asynergy by nitroglycerin in coronary artery disease

To evaluate the potential reversibility of left ventricular asynergy in patients with coronary artery disease, pre- and postnitroglycerin left ventriculography was performed in 32 subjects. In four other subjects left ventriculography was repeated without intervention of nitroglycerin. Changes in ejection fraction and percentage of systolic shortening of three minor axes from the first to the second angiogram were then calculated. Changes were not significant for the myocardial infarction group or for the control group without the intervention of nitroglycerin. Normal left ventricles showed small but significant changes (p less than 0.05). Patients with coronary artery disease but without previous myocardial infarction who demonstrated asynergy in their first angiogram showed three types of response: (1) no significant change (p less than 0.05)-irreversible asynergy; (2) significant change (p less than 0.025) with residual dysfunction-partially reversible asynergy; (3) significant change (p less than 0.001) without residual dysfunction-completely reversible asynergy. It is concluded that postnitroglycerin ventriculography is useful in assessing the reversibility of left ventricular asynergy in patients with coronary artery disease.

Comparative hemodynamic effects of chewable isosorbide dinitrate and nitroglycerin in patients with congestive heart failure

Vasodilators are known to be effective in improving the hemodynamics of congestive heart failure by increasing cardiac output and reducing left ventricular filling pressure (LVFP). Long acting agents are needed to augment the practicality and availability of chronic vasodilator therapy. In the present study the vascular effects of chewable isosorbide dinitrate (CHIS), sublingual nitroglycerin (NTG) and placebo (P) were compared in eight patients with high LVFP due to heart failure. Patients with LVFP (pulmonary wedge pressure) over 14 mm Hg were given CHIS, 10 mg, NTG, 0.6 mg, and P, two chewable tablets, in random fashion. Heart rate (HR), blood pressure (BP) and LVFP were monitored for three hours after each drug. HR was not significantly affected by any drug, although it rose slightly after NTG and fell after CHIS. Significant reduction of BP occurred only after NTG, with peak effect at five minutes, but lasting only 15 minutes. NTG reduced LVFP 5.1 mm Hg (19.5%, P, less than 0.05), at peak effect, but LVFP was no longer significantly lower by 20 minutes after NTG. After CHIS, LVFP fell significantly within five minutes, reached a peak reduction of 8.6 mm Hg (32;7%, P less than 0.01) at 15 minutes, and remained significantly lower through three hours. Thus CHIS provides a nitrate action of rapid onset and sustained effect that may be useful for chronic vasodilator therapy of heart failure.

Effects of nitroglycerin on transmural myocardial blood flow in the unanesthetized dog

This study was designed to determin the effect of nitroglycerin upon transmural distribution of myocardial blood flow in the awake dog during normal conditions and in the presence of ischemia-induced coronary vasodilation. Studies were performed in chronically prepared dogs with electromagnetic flowmeters and hydraulic occluders on the left circumflex coronary artery. Regional myocardial blood flow was estimated by using radionuclide-labeled microspheres, 7-10 mum in diameter, injected into the left atrium. During control conditions endocardial flow (0.86 plus or minus SEM 0.05 ml/min per g) slightly exceeded epicardial flow (0.72 plus or minus 0.03 ml/min per g, P smaller than 0.05), and this distribution of flow was not significantly altered by nitroglycerin. After a 5-s coronary artery occlusion, reactive hyperemia occurred with excess inflow of arterial blood effecting 360 plus or minus 15% repayment of the blood flow debt incurred during occlusion. When arterial inflow was limited to the preocclusion rate during coronary vasodilation after a 5-s total coronary artery occlusion, flow to the subepicardial myocardium was increased at the expense of underperfusion of the subendocardial myocardium, and the delayed reactive hyperemia was markedly augmented (mean blood flow debt repayment =775plus or minus 105%, P smaller than 0.01). Tese data suggested that subendocardial underperfusion during the interval of coronary vasodilation in the presence of a flow-limiting proximal coronary artery stenosis caused continuing subendocardial ischemia which resulted in augmentation of the reactive hyperemic response. In this experimental model both the redistribution of myocardial blood flow which occurred during an interval of restricted arterial inflow after a 5-s coronary artery occlusion and augmentation of the subsequent reactive hyperemic response were returned toward normal by nitroglycerin. This effect of nitroglycerin may have resulted, at least in part, from its ability to vasodilate the penetrating arteries which deliver blood from the epicardial surface to the subendocardium.

Hemodynamic effects of nitroglycerin in acute myocardial infarction

Nitroglycerin (NTG) has recently been suggested to decrease myocardial ischemia and enhance cardiac pump function during acute myocardial infarction (AMI). To evaluate the sublingual agnet in this condition, the hemodynamic effects of 0.4 mg NTG administered to 16 supine patients during the first 72 hours of AMI were determined serially 5, 10 to 15, and 20 to 30 minutes post-NTG. Data were evaluated for the entire group, as well as for six patients with normal pulmonary artery wedge pressure (PAW) (less than or equal to 12 mm Hg; mean 7) who formed group I and for ten patients with elevated PAW (greater than 12 MM Hg; mean 19) who comprised group II. In the 16 patients, NTG resulted in significant decreases in PAW (14 TO 7 MM Hg; P less than .01), mean systemic arterial pressure (MAP) (95 TO 82 MM Hg; P less than .01), cardiac index (CI) (1.79 TO 1.46 L/min/m-2; P less than .02), stroke index (SI) (24 TO 18 CC/M-2; P less than .01) and stroke work index (SWI) (27 TO 20 GM TIMES M/M-2; P less than .01). These alterations were significant in both subgroups, with the decline in PAW greater (P less than .05), while there was no change in group II. There was no significant change in total peripheral vascular resistance (TPVR) for the entire group or in the two subgroups. This study demonstrates that, regardless of initial left ventricular filling pressure, sublingual NTG given in the acute phase of AMI results in rapid fall in PAW, concomitant with decreases in systemic blood pressure, cardiac output and SWI, without changes in TPVR and with little or no effect on heart rate. Since TPVR was unaltered, the decline in MAP was due to fall in cardiac output. Thus, the principal action of sublingual NTG in AMI appears to be systemic venodilation with consequent reduction of ventricular preload. This effect is translated into decline ofpump output even in patients with high initial filling pressures. Although NTG may rapidly relieve pulmonary congestion and lower myocardial oxygen consumption, use of the agent sublingually is limited in AMI because these salutary effects are accomppanied by potentially deleterious fall in cardiac output and systemic blood pressure.

Polygraphic studies of the effect of nitroglycerin in patients with ischaemic heart disease

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Medical management of angina pectoris

The successful medical management of a patient with angina pectoris requires careful attention to many factors including omission of smoking, control of hypertension, and weight reduction for the obese person. Newer knowledge of the importance of the product of the systolic blood pressure and the pulse rate in determining the threshold of angina affords a more meaningful approach to therapy. Each individual must be educated regarding the factors that aggravate and precipitate his distress so that these can be minimized, or prophylactic nitrite therapy can be appropriately applied. Emotional stress is of equal importance to effort in the production of angina. The mainstay stay of treatment is nitroglycerin and sublingual nitrites combined with beta-blocking drugs. Each drug or combination must be properly readjusted for the individual to assure optimum benefit. Digitalis, diuretics, antiarrhythmic drugs, antihypertensive agents, and radioiodine may be useful in selected cases.

Influence of nitroglycerin on myocardial metabolism and hemodynamics during angina induced by atrial pacing

Myocardial lactate extraction, arterial-coronary sinus difference (A-CS) of potassium (K + ), hemodynamics, and S-T segments were studied in 15 patients with coronary artery disease who developed angina during atrial pacing. The study consisted of the following periods: control (C 1 ), pacing (P 1 ), recovery (C 2 ), control after nitroglycerin (C GTN ), second pacing (P 2 ), and recovery. During C 1 , mean lactate extraction, S-T segments, and left ventricular end-diastolic pressure (LVEDP) were normal, and there was no myocardial K + loss. During P 1 the mean lactate production was –12.0%, mean K + loss –0.26 mEq/liter, and mean S-T segment depression 1.97 mm, while the average LVEDP remained unchanged, increasing when pacing was discontinued to a mean value of 23.3 mm Hg. These values returned to control levels by the time GTN was administered. After GTN there were significant decreases in mean cardiac index, LVEDP, brachial artery pressure, and left ventricular stroke work. During P 2 , eight subjects had no pain, five experienced less severe angina, mean lactate production and K + loss were abolished, S-T segments became less depressed (0.8 mm), and mean LVEDP decreased during pacing, rising only to 11.4 mm Hg when pacing was discontinued. Myocardial lactate production reverted to extraction in two patients and decreased in another two, whereas seven patients showed a decreased K + loss or uptake. It is concluded that GTN may prevent or reduce pacing-induced angina, as well as improve the electrocardiogram and hemodynamics, and in some patients decrease myocardial anaerobiosis.