Letter to the Editor: Reassessing intravenous antihypertensive choice in coronary artery disease-related hypertensive emergencies

Abstract

Hypertensive emergencies in patients with established coronary artery disease (CAD) present a therapeutic paradox, that blood pressure must be lowered rapidly to limit end-organ damage, yet excessive or poorly selected pharmacologic intervention risks myocardial ischemia and adverse cardiovascular outcomes. In this context, a study by Chaudhary et al, published in the recent issue of the World Journal of Cardiology, provide novel and clinically interesting real-world data comparing intravenous nitroglycerin and labetalol in a large retrospective cohort of CAD patients presenting with hypertensive emergency. Their analysis demonstrates a nuanced trade-off between hemodynamic speed and cardioprotective benefit. While labetalol achieved target blood pressure more rapidly, nitroglycerin was associated with greater absolute blood pressure reduction, fewer bradyarrhythmic events, attenuated cardiac biomarker elevation, shorter intensive care unit and hospital stays, and lower 30-day readmission rates. Although major adverse cardiovascular events did not differ significantly, the observed trends favoring nitroglycerin underscore the importance of ischemia-sensitive blood pressure management in this high-risk population. Importantly, these findings align with the contemporary guideline principles that prioritize myocardial perfusion and preload reduction in CAD-associated hypertensive crises. Despite the inherent limitations of the retrospective, single-center analyses, this study advances the evidence base by focusing specifically on CAD patients in a resource-constrained setting and by incorporating clinically meaningful utilization outcomes. Collectively, the data support a more deliberate, phenotype-driven approach to agent selection in hypertensive emergencies, positioning nitroglycerin as a preferential option when myocardial ischemia is a central concern, while reinforcing the need for prospective, randomized validation.

Key Words: Hypertensive emergencies; Coronary artery disease; Nitroglycerin; Labetalol; Intravenous antihypertensive therapy; Myocardial ischemia

Core Tip: Chaudhary et al provide large real-world evidence in coronary artery disease-associated hypertensive emergency comparing intravenous nitroglycerin with labetalol. Labetalol achieved target blood pressure faster, but nitroglycerin produced greater blood pressure reduction, fewer bradycardic events, smaller biomarker rises, shorter intensive care unit/hospital stays, and fewer 30-day readmissions. These results support phenotype-driven therapy, that labetalol when heart rate control is paramount, and nitroglycerin when ischemia, pulmonary congestion or myocardial injury risk dominate. Prospective validation is required before practice-changing recommendations.

TO THE EDITOR

Hypertensive emergency is defined not solely by severe blood pressure elevation but by the presence of acute end-organ injury requiring immediate parenteral therapy and careful monitoring[1]. In patients with established coronary artery disease (CAD), the syndrome is especially precarious because elevated afterload increases myocardial oxygen demand at a time when coronary flow reserve is often impaired by fixed stenoses, endothelial dysfunction, and microvascular disease[2]. At the same time, overly aggressive blood pressure lowering can compromise coronary perfusion pressure, particularly in patients with left ventricular hypertrophy, multivessel CAD or diastolic dysfunction, thereby precipitating demand ischemia, electrical instability, or frank infarction. Consequently, management priorities in CAD-associated hypertensive emergencies extend beyond simply lowering a numeric blood pressure value[3]. The therapeutic goal is rapid stabilization while preserving myocardial perfusion, preventing ischemia and avoiding drug-induced bradycardia or decompensated heart failure.

Although guideline frameworks emphasize controlled reduction of blood pressure, often approximately 20%-25% of mean arterial pressure in the first hour for many presentations, the evidence base that specifically guides drug selection in CAD-associated hypertensive emergencies remains limited[3]. Much of contemporary practice is extrapolated from mixed-population hypertensive crisis studies or from neurologically driven hypertensive emergency cohorts, where therapeutic aims and the risk-benefit balance differ substantially from those in coronary disease. Therefore, real-world comparative effectiveness data in CAD patients have practical value, particularly when they incorporate both physiologic outcomes and healthcare utilization endpoints.

In this context, a study by Chaudhary et al[4], published in the recent issue of the World Journal of Cardiology, present an important single-center retrospective cohort analysis from Pakistan comparing intravenous nitroglycerin and labetalol in 563 patients with established CAD presenting with hypertensive emergency over the period 2018-2024. Their primary endpoint was time to reach blood pressure control, defined as systolic blood pressure below 160 mmHg and diastolic blood pressure below 100 mmHg. The investigators report that labetalol achieved this target more rapidly than nitroglycerin, with mean times of approximately 25 minutes and 30 minutes respectively, a statistically robust difference. However, when interpreting this finding clinically, the magnitude of the time advantage may not be equally important across end-organ phenotypes. In CAD, where ischemia avoidance and myocardial protection are central priorities, the speed of blood pressure lowering must be balanced against the physiologic consequences of the drug used to achieve it[5].

A striking feature of the study is that nitroglycerin, despite a modestly slower time-to-target, produced greater absolute reductions in both systolic and diastolic blood pressures. More importantly, nitroglycerin was associated with clinically meaningful safety and cardiac-protection signals, including a substantially lower rate of bradycardia than labetalol and smaller rises in cardiac biomarkers. The bradycardia difference, approximately 2% with nitroglycerin compared with 10% with labetalol, has immediate bedside relevance in CAD populations that frequently include older adults with conduction system disease, beta-blocker sensitivity, or borderline cardiac output reserve. Additionally, the observation that delta troponin and N-terminal proBNP increases were attenuated in the nitroglycerin group provides mechanistic plausibility for a myocardial-protective effect during hypertensive crisis, even if hard cardiovascular endpoints were not statistically different in this observational dataset.

Beyond physiologic measures, the study adds value by incorporating utilization endpoints that are often omitted from hypertensive emergency research. Patients treated with nitroglycerin had shorter intensive care unit and hospital lengths of stay and lower 30-day readmission rates. Major adverse cardiovascular events were similar between groups, although adjusted analyses suggested a non-significant trend favoring nitroglycerin. The combination of reduced bradyarrhythmia burden, more favorable biomarker trends, and lower healthcare utilization strengthens the argument that, in CAD-associated hypertensive emergencies, the optimal agent may be the one that best stabilizes myocardial oxygen supply-demand balance rather than the one that simply achieves a blood pressure target fastest.

These results are pharmacologically coherent. Nitroglycerin primarily reduces preload through venodilation and lowers left ventricular wall stress, thereby reducing myocardial oxygen demand while potentially improving subendocardial perfusion[6-8]. Such properties are highly desirable when myocardial ischemia, pulmonary congestion, or acute coronary syndrome physiology is present or suspected. In contrast, labetalol’s alpha- and beta-blocking effects lower blood pressure and reduce heart rate, which can be beneficial in adrenergically mediated hypertensive crises, tachycardia-dominant ischemia, or situations where heart rate control itself is the primary therapeutic objective[9-11]. Yet, the same beta-blockade that improves diastolic time and oxygen demand can also precipitate clinically significant bradycardia in vulnerable individuals and may be less favorable in patients with conduction abnormalities or reduced cardiac output reserve[12-14]. The bradycardia signal observed by Chaudhary et al[4] therefore aligns with established pharmacodynamic concerns.

The practical implication is that these data support a phenotype-driven approach to intravenous antihypertensive selection rather than a universal hierarchy between agents. In CAD patients with hypertensive emergency who present with chest pain suggestive of ischemia, evolving troponin rise, pulmonary congestion, or high likelihood of demand-mediated myocardial injury, nitroglycerin appears particularly well positioned as an initial agent given its preload reduction and anti-ischemic potential, in addition to effective blood pressure lowering[15]. Conversely, in CAD patients where adrenergic surge and marked tachycardia are dominant, labetalol may be preferable due to its heart rate control and afterload reduction, provided that bradycardia risk is carefully assessed and monitored[16-18]. In patients with known conduction system disease, baseline bradycardia or severe left ventricular dysfunction, the study’s findings encourage a more cautious stance regarding labetalol and greater consideration of nitroglycerin-based strategies[19,20].

At the same time, readers must interpret the results within the limitations of the retrospective comparative effectiveness research. Treatment allocation was not randomized and indication bias is likely, because clinicians may preferentially select nitroglycerin for ischemic presentations and labetalol for tachycardia or pain syndromes. Indeed, the baseline distribution of clinical features such as chest pain differed between groups, suggesting potential confounding by presentation phenotype. Dose titration heterogeneity, crossover to other agents, or adjunctive therapies may also influence outcomes in ways that are difficult to fully adjust for. The single-center setting limits its applicability across the health systems and follow-up was limited to 30-day readmission and early events, leaving longer-term clinical consequences uncertain. Additionally, an adjusted but non-significant signal toward higher stroke odds with nitroglycerin, though likely confounded and statistically imprecise, appropriately highlights that hypertensive emergency therapy must remain organ-specific and that cerebral autoregulation considerations cannot be ignored in mixed presentations.

Despite these limitations, Chaudhary et al[4] provide a clinically actionable dataset that is particularly valuable in regions with limited evidence and high CAD burden. Their findings encourage clinicians to reconsider default reliance on beta-blockade as the primary intravenous strategy for all CAD-associated hypertensive emergencies and instead to align therapy with the dominant threatened organ system and the patient’s conduction and myocardial injury risk profile. Importantly, the study suggests that nitroglycerin may carry advantages that matter to both patients and health systems, including reduced bradyarrhythmia events and lower resource utilization.

FUTURE DIRECTIONS

Future research should build upon this foundation with prospective trials specifically enrolling CAD patients with hypertensive emergencies and stratifying them by ischemic vs non-ischemic presentation, pulmonary congestion and baseline conduction characteristics. Randomized comparisons with standardized titration protocols would clarify whether nitroglycerin’s favorable biomarker and utilization profile translates into definitive reductions in infarction, heart failure progression and longer-term cardiovascular events. Serial biomarker assessment linked to imaging endpoints, such as echocardiography or perfusion evaluation, may further define mechanistic pathways and identify responders. Pragmatic trials could also evaluate combination strategies, in which nitroglycerin is used for preload and ischemia control while cautious beta-blockade is added selectively for tachycardia, potentially reconciling the hemodynamic speed advantage of labetalol with the myocardial-protective benefits of nitrates.

CONCLUSION

In conclusion, Chaudhary et al[4] offer meaningful real-world evidence addressing an under-studied but clinically important scenario, the drug selection for hypertensive emergency in patients with CAD. While labetalol achieves target blood pressure more rapidly, nitroglycerin appears to offer a more favorable safety and utilization profile, with fewer bradycardic events, attenuated troponin rise, shorter ICU and hospital stays, and fewer 30-day readmissions. These data support the phenotype-driven therapy, labetalol for tachycardia-dominant or adrenergic presentations when bradycardia risk is low, and nitroglycerin when myocardial ischemia, pulmonary congestion, or myocardial injury risk dominates. The findings are hypothesis-generating and reinforce the need for prospective, randomized validation before definitive guideline-level recommendations can be made.