Revenue
| | | | | | | | | | | | |
| | Revenue by Geography | |
| | Year ended | | | | | | |
| | December 31, | | Change | |
(in thousands) | | 2024 | | 2023 | | $ | | % | |
United States | | $ | 47,167 | | $ | 35,111 | | $ | 12,056 | | 34 | % |
Europe | | | 4,125 | | | 4,184 | | | (59) | | (1) | % |
Total Revenue | | $ | 51,292 | | $ | 39,295 | | $ | 11,997 | | 31 | % |
Revenue was $51.3 million for the year ended December 31, 2024, an increase of $12.0 million, or 31%, over the year ended December 31, 2023.
Revenue generated in the U.S. was $47.2 million for the year ended December 31, 2024, an increase of $12.1 million, or 34%, over the year ended December 31, 2023. HF revenue units in the U.S. totaled 1,506 and 1,123 for the years ended December 31, 2024 and 2023, respectively. HF revenue in the U.S. totaled $46.8 million and $34.6 million for the years ended December 31, 2024 and 2023, respectively. The increase was primarily driven by continued growth as a result of the expansion into new sales territories and new accounts, as well as increased physician and patient awareness of Barostim.
As of December 31, 2024, we had a total of 223 active implanting centers in the U.S., as compared to 178 as of December 31, 2023. Active implanting centers are customers that have completed at least one commercial HF implant in the last 12 months. As of December 31, 2024, we had 48 sales territories in the U.S. as compared to 38 sales territories as of December 31, 2023.
Revenue generated in Europe was $4.1 million for the year ended December 31, 2024, a decrease of $0.1 million, or 1%, over the year ended December 31, 2023. Total revenue units in Europe decreased to 204 for the year ended December 31, 2024, from 207 for the prior year. As of December 31, 2024, we had five sales territories in Europe as compared to six sales territories as of December 31, 2023.
Cost of goods sold and gross margin
Cost of goods sold increased $2.1 million, or 33%, to $8.3 million for the year ended December 31, 2024, compared to the year ended December 31, 2023. This increase was primarily due to higher sales of Barostim.
Gross profit was $43.0 million for the year ended December 31, 2024, an increase of $9.9 million, or 30%, over the year ended December 31, 2023. Gross margin was 84% for both the years ended December 31, 2024 and 2023.
Research and development expenses
R&D expenses decreased $0.5 million, or 4%, to $11.1 million for the year ended December 31, 2024, compared to the year ended December 31, 2023. This change was primarily driven by a $0.5 million decrease in consulting expenses, a $0.3 million decrease in compensation expenses, and a $0.2 million decrease in travel expenses, partially offset by a $0.5 million increase in clinical study expenses.
Selling, general and administrative expenses
SG&A expenses increased $26.8 million, or 42%, to $91.3 million for the year ended December 31, 2024, compared to the year ended December 31, 2023. This change was driven by a $12.7 million increase in non-cash stock-based compensation expense, an $11.0 million increase in compensation expenses, mainly as a result of increased headcount, a $1.3 million increase in travel expenses, a $0.6 million increase in bad debt expenses, and a $0.5 million increase in consulting expenses. Approximately $8.4 million of the increase in non-cash stock-based compensation expense is related to the modification of stock options held by our